Rtm molding method and device

ABSTRACT

An RTM molding method and device includes disposing a reinforcing fiber substrate in a cavity of a mold consisting of a plurality of dies, clamping the mold, and injecting resin to complete molding, wherein divided areas with respect to the surface direction of the reinforcing fiber substrate are assumed, each divided area is one in which injected resin expands over the entire surface in the area and can be substantially uniformly impregnated in the thickness direction of the substrate, and resin introducing paths are formed for respective assumed divided areas to introduce injected resin into the respective divided areas. When a relatively large molded product is molded, a molding step from resin injection to impregnating/curing can be implemented at high speed without generating a non-resin-flowing area, thereby producing a high-quality molded product with a shortened molding time and increased production speed and volume.

RELATED APPLICATION

This is a divisional application of U.S. application Ser. No. 10/589,589filed Aug. 16, 2006, which is a §371 of International Application No.PCT/JP2005/02314, with an international filing date of Feb. 16, 2005 (WO2005/077632 A1, published Aug. 25, 2005), which is based on JapanesePatent Application Nos. 2004-39882 filed Feb. 17, 2004; 2004-63777 filedMar. 8, 2004 and 2004-281611 filed Sep. 28, 2004, the subject matter ofwhich is incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to RTM (Resin transfer Molding) molding methodand device for molding a relatively large FRP (Fiber ReinforcedPlastic), and more specifically, to RTM molding method and devicecapable of achieving a high-speed molding and improving a surfacequality.

BACKGROUND

FRP, in particular, CFRP (carbon fiber reinforced plastic), is utilizedin various fields as a composite material having a property light inweight and high mechanical properties. As one of FRP molding methods, anRTM molding method is known wherein a reinforcing fiber substrate suchas a laminated substrate of reinforcing fiber woven fabrics is placed ina mold, and after the mold is clamped, a liquid resin is injected intothe mold reduced in pressure, and the resin is heated and cured.Further, in such a conventional molding, it is proposed to give acertain shape to a reinforcing fiber substrate before disposing it in amold by clamping it with upper and lower preforming dies (for example,JP-A-2003-305719).

In a conventional RTM molding method, generally resin is injected at apressurized condition from a single injection port. Then, as the casemay be, a plurality of resin discharge ports are provided. In such aconventional method, however, there is a problem that RTM molding of alarge product is difficult, because it is difficult to set a largeamount of flowing resin and there is only one resin injection port.Namely, gelation of resin progresses (resin viscosity increases) duringresin flowing, and there occurs a case where the resin does not flowover the entire area of a product to be molded. Further, if the time ofgelation is extended by adding a delay agent to the resin, it ispossible to flow the resin over the entire area although a long time isrequired, but too much time is required for achieving a predeterminedresin flow, thereby decreasing the production speed and the productionamount. Furthermore, when a large product, in particular, a relativelylarge three-dimensional plane-like product is molded, if resin is flownfrom a single injection port, in accordance with the shape, there mayoccur an area where the resin does not flow. Even if the resin flow iscontrolled by providing a plurality of resin discharge ports, there is alimit for molding a complicated structure properly.

On the other hand, as a method for carrying out resin injection at atime from the entire surface of a product to be molded, there is an RFI(Resin Film Infusion) method. In this method, non-impregnatedreinforcing fiber substrate applied with a semi-cured resin film isheated, and molten resin is impregnated by pressing it by hot press andthe like, but a complicated-shape molding is difficult, and there is aproblem that a non-impregnated portion is liable to occur in a part ofthe reinforcing fiber substrate.

As a method of impregnation even for a product to be molded which iscomplicated to some extent and large, there is a method described inJP-A-2002-234078. In this method, a carrier of a matrix resin, forexample, prepared by impregnating a molten resin into a sponge material,is used instead of the resin film in the aforementioned RFI method, andalthough it is an improved method, because a method for covering theentire product to be molded with a bagging film and reducing in pressurethe inside thereof is employed as a method for achieving pressureimpregnation for a large product in an inexpensive and easy manner, apressurizing force of only 0.1 MPa can be generated at maximum, andtherefore, there are problems that impregnation for a thick product isdifficult and that impregnation up to detailed portions is difficult.

Since any of these methods is not a method for impregnating a matrixresin into a reinforcing fiber substrate while flowing the molten resinfrom initial time, there left a cause for generating non-impregnatedportions.

Further, as a conventional RTM molding method, a method is also knownwherein resin is injected at a pressurized condition from a singleinjection line. For example, when a product to be molded has a shape ofa polygon (a shape with a plurality of sides), the resin is injectedfrom a certain one side toward another side opposite to the certain oneside (for example, JP-A-8-58008 and JP-A-2003-11136). In such a method,however, although the resin surely flows from one side toward theopposite side while the resin is impregnated into a reinforcing fibersubstrate in order, if the product to be molded is relatively large, ittakes much time to flow the resin, and as the case may be, the resin mayreach a time of its gelation during its flow, in such a condition thereis a problem that the resin flow stops before complete impregnation.Accordingly, as described in the aforementioned JP-A-8-58008, a methodfor providing resin injection lines at a plurality of positions of aproduct to be molded and injecting the resin in order is proposed. Inthis method, however, since the resin is injected from portions within amolding area of the product to be molded, it cannot be applied to asandwich molded product using a core material and disposing reinforcingfiber substrates on both surfaces of the core material, because theresin cannot be injected from a mold surface side. Further, even in acase of a non-sandwich molded product, the method cannot be applied tothe molding of a product which is double-sided and which requires a highdesign quality for its surface. Thus, in the above-describedconventional RTM molding methods, it is difficult to efficiently mold arelatively large product.

Usually, in an RTM mold consisting of relatively many dies, there is abig problem that the productivity is low, because the molding takes muchtime. On the other hand, in a structure of a mold consisting of an upperdie and a lower die, although it has an advantage that theaforementioned setting of a reinforcing fiber substrate onto the surfaceof the mold is relatively easy and the setting time is short, in a caseof a general resin injection method, that is, in a case where resin ispressurized at a pressure of 0.2 to 1.0 MPa and the resin is injectedwithout a particular control of flow rate, the resin flows into the moldat a flow rate corresponding to the pressure and the resin is charged inthe mold in a relatively short period of time, but there may occur acase where the reinforcing fiber substrate is disturbed by the resinflow, or where a non-uniform flow occurs by a high flow rate and manyvoids and pinholes are generated on the surface of a molded product.

In particular, in a case where resin injection is carried out at a highresin discharge pressure of 0.5 MPa or more (therefore, at a high flowrate) to shorten a molding time or to mold a product having a large areain a short period of time, disturbance of the weave structure of areinforcing fiber substrate (particularly, a plain weave fabric) isliable to occur, and further, because the resin flows in the mold at ahigh speed, the resistance against the flow disperses within the flowarea depending upon a dimensional unevenness (particularly, anunevenness in thickness) of a cavity in the mold, a fine unevenness inthickness of the substrate, or a difference between partial structuresof the substrate due to overlapping of substrate layers and the like,and because a uniform flow cannot be maintained, there is a case where alarge void is generated by occurrence of a local forestalling of theresin flow and the like. Furthermore, there is a case where the resinactually flows up to the substrate portion, but, because the flow rateis high, for example, there is no time for release of gas present in thetexture of the woven fabric and the gas stays there, and the gasgenerates a surface defect such as a pinhole. In such conventionalmolding conditions and molding process causing reduction of quality inappearance concerning the design quality such as substrate disturbance,voids and pinholes, it is difficult to ensure a high surface qualitywhile carrying out a high-speed injection for shortening the moldingtime. The larger the size of a product to be molded becomes, the morefrequently such defects on quality in appearance are liable to occur,because a high-speed resin injection is to be inevitably employed.

Because the flow state of resin greatly influences generation of suchvoids and pinholes concerning design quality, the density of thereinforcing fiber substrate, that is, the weight thereof, also becomesan important factor. Namely, because a weight of reinforcing fibers perone layer influences a flow resistance of resin and easiness of gasrelease, it is necessary to set a proper weight in accordance with theresin flow condition. This proper weight has to be set from theviewpoints of not only the surface quality but also the workability andutilization factor in strength of a pre-form. Namely, if the weight istoo great and the rigidity of the substrate becomes high, therein-forcing fiber substrate becomes hard to be situated along the moldsurface and hard to be formed in a three-dimensional shape, and there isa case where it takes much working time to make a pre-form, or that atthat time disturbance of the substrate occurs and the mechanicalproperties of the FRP molded product decrease. Namely, to carry out anefficient production, there is a proper weight corresponding to theproduction conditions (molding size shape, molding conditions, etc.).

Further, among molding conditions, particularly influence given to asurface quality by temperature and resin injection pressure is great. Ifa temperature of injected resin itself or a resin temperature heated bya mold is high, the resin viscosity reduces and the flowability of theresin increases, and although the impregnation property of the resininto the substrate is good, the flowability rapidly deteriorates by ahigh elevation rate of the viscosity, and when the molded product isbig, there is a case where the flow of the resin reduces in speed on theway of the molding and it causes a non-impregnated portion. Even if theresin can flow over the entire area, in an area in which the viscosityhas become high, there is a case where many voids and pinholes aregenerated even though non-impregnated portions are not generated. On theother hand, if there is an unevenness of the temperature of a mold orthere is a change in the temperature during molding, there is a casewhere very fine gas bubbles remaining in the mold come into contact witheach other and they grow a big bubble developing to a void or a pinhole.

Further, it is important that the pressure is also adequate. Namely, ifthe pressure is too high, the resin flow rate becomes high, and there isa case where it causes a disturbance of the weave structure of thesubstrate or it causes an expansion in volume in a cavity to generatebubbles, and if the pressure is too low, there is a case where residualbubbles cannot be compressed to be small.

Further, since a reactive gas may be generated from a reactive resin inits curing process, or fine gas (bubbles) having been contained in aresin may grow to voids or pinholes as the molding time passes, it isbetter to cure the resin as quickly as possible after the resin isimpregnated into the substrate.

The influence given to the yield of the molding by the characteristicsof the material of the reactive resin is very high, and for example,depending upon the kind of the curing agent, the reaction speed becomesmaximum at an initial period of the reaction of the resin, andthereafter, the time passes. Therefore, the reaction speed reduces, andthere is a case where the time required for the curing becomes long. Onthe contrary, if the curing time is to be shortened by elevating thetemperature of the mold, there is a case where the initial viscosityincreases too much, the viscosity is elevated too much at the time ofresin injection and flow, ultimately the resin is gelated, and themolding is stopped on the way and a non-impregnated portion isgenerated.

Thus, in FRP molding (particularly, RTM molding), there exist propermolding conditions and material characteristic in accordance withmolding size (area), and if not molded at proper conditions, problems onquality, in particular, on surface quality, are liable to occur.

Further, to improve the surface quality of a molded product as one ofthe purposes, a method is proposed wherein a reinforcing fiber substrateis given with a certain shape before it is disposed in a mold, bynipping it with upper and lower dies for preforming prior to RTMmolding, and only the reinforcing fiber substrate preformed is disposeddirectly on the molding surface (for example, the aforementionedJP-A-2003-305719).

In such a conventional molding method, however, if a resin to beinjected and cured is not delivered enough and is not impregnated intothe details of the reinforcing fiber substrate, voids and pinholes mayoccur, and the mechanical properties of the molded product may bedecreased, or the surface quality may be reduced. Especially, if voidsor pinholes appear on the surface, in particular, on the design surfaceside, although usually patching such as charge of resin is carried out,this patching requires work and time, and decreases the efficiency ofthe whole of the manufacturing process.

As the countermeasure for preventing occurrence of such voids andpinholes injuring the design quality of the design surface, there is acase where a random mat layer is provided on the upper surface of asurface-layer substrate. This random mat layer is called as “a surfacemat” because the random mat layer becomes an outermost layer, andparticularly in a prepreg/autoclave curing method, an RFI (Resin FilmInfusion) method, a hand-lay-up method, etc., it is sometimes employed.However, the structure thereof is a substrate structure in which thesurface substrate and the random mat layer are completely replaced witheach other, as compared the embodiment described later.

In a case where such a substrate structure is employed in a moldingmethod such as RTM molding and vacuum molding wherein a resin fluid isinjected into a dry substrate and flown and impregnated into thesubstrate, it is necessary to discharge also bubbles by the flow of theresin, and at a portion with a low resin flowability, voids are liableto be generated or pinholes are liable to occur by the left bubbles.

In a case where an FRP is molded by an RTM molding method or a vacuummolding method by using the above-described random mat as a surface matand disposing it as an outermost layer, the random mat in a state of adry substrate is pressed to the mold surface, and a gap between the moldsurface and the random mat is very small because the bulkiness of therandom mat with a low weight is low. Therefore, the resin flowabilityinto the gap is poor, and as a result, voids and pinholes are liable tooccur at the position thereof. Thus, particularly in an RTM moldingmethod and a vacuum molding method, even if a random mat layer isprovided as an outermost layer (a surface layer at a design surface),occurrence of voids and pinholes cannot be prevented.

Accordingly, paying attention to the above-described situations, itcould be helpful to provide an RTM molding method and device wherein,even as for a relatively large three-dimensional configuration, themolding process from resin injection to impregnation and curing can becarried out at a high speed as compared with conventional RTM moldingmethod and device, without generating non-resin-flowing areas, therebyachieving shortening of the molding time, increase of production speedand production amount, in particular, increase of production amount perone mold, and reducing the production cost.

Further, it could be helpful to provide an RTM molding method and devicewherein, in an RTM molding for molding a relatively large fiberreinforced plastic product with a projection area of substantially 1 m²or more, a voidless high-quality product can be molded efficiently in ashort period of time.

Furthermore, it could be helpful to provide an RTM molding methodwherein injected resin can be surely and easily delivered over theentire range of a desirable area in the resin injection step, and afiber reinforced plastic with an improved surface quality can beproduced by preventing occurrence of voids and pinholes on a surface, inparticular, on the design surface side.

SUMMARY

We provide an RTM molding method comprising the steps of disposing areinforcing fiber substrate in a cavity of a mold consisting of aplurality of dies, clamping the mold, and thereafter injecting resin tocomplete molding, and characterized in that divided areas with respectto a surface direction of the reinforcing fiber substrate are assumed,each divided area is one in which injected resin expands over the entiresurface in each divided area and can be substantially uniformlyimpregnated in a thickness direction of the substrate, and resinintroducing paths are formed for respective assumed divided areas forintroducing the injected resin into the respective divided areas. Inthis RTM molding method, vacuum suction may be carried out from a resindischarge line for a predetermined period of time of at least from atime after clamping the mold to a time starting resin injection.

Further, we provide an RTM molding device for disposing a reinforcingfiber substrate in a cavity of a mold consisting of a plurality of dies,clamping the mold, and thereafter injecting resin to complete molding,is characterized in that divided areas with respect to a surfacedirection of the reinforcing fiber substrate are assumed, each dividedarea is one in which injected resin expands over the entire surface ineach divided area and can be substantially uniformly impregnated in athickness direction of the substrate, and resin introducing paths areformed for respective assumed divided areas for introducing the injectedresin into the respective divided areas. In this RTM molding device, thedevice may have means for carrying out vacuum suction from a resindischarge line for a predetermined period of time of at least from atime after clamping the mold to a time starting resin injection.

In the above-described RTM molding method and device, for a reinforcingfiber substrate with a relatively large area, adequate divided areas areassumed, resin introducing paths are formed for respective assumeddivided areas for introducing the injected resin into the respectivedivided areas, and by injecting the resin via the resin introducingpaths, as the result, the resin is impregnated quickly and uniformlyover the entire range of the reinforcing fiber substrate. The number ofdivision of the divided areas may be a countable number as shown in thefirst and second embodiments described later, or may be substantially.

Then, we provide an RTM molding method wherein an intermediate memberhaving resin paths extending through the intermediate member in itsthickness direction is disposed between dies forming the mold, and resinis injected to the reinforcing fiber substrate from a plurality ofpositions via the intermediate member almost simultaneously (methodaccording to a first embodiment).

Further, we provide an RTM molding device wherein an intermediate memberhaving resin paths extending through the intermediate member in itsthickness direction is disposed between dies forming the mold forinjecting resin to the reinforcing fiber substrate from a plurality ofpositions via the resin paths almost simultaneously (device according toa first embodiment).

In the RTM molding method and device according to the first embodiment,a structure may be employed wherein a groove for discharging resin,which extends substantially over the entire circumference of thereinforcing fiber substrate, is formed on any one of the dies. Further,a structure may also be employed wherein a groove for discharging resin,which extends substantially over the entire circumference of thereinforcing fiber substrate, is formed on the above-describedintermediate member.

The above-described intermediate member may be structured to be providedwith grooves for resin paths formed on its one surface and through holescommunicating with the grooves and extending to its reinforcing fibersubstrate disposed-side surface opposite to the above-described onesurface through the intermediate member.

The above-described intermediate member can be made from either a metalor a resin. Further, a structure can be employed wherein a member forresin injection (for example, a pipe for resin injection) is nipped andsealed by the intermediate member and a die facing the intermediatemember. Further, a structure can also be employed wherein a member forresin discharge (for example, a pipe for resin discharge) is nipped, andsealed by the intermediate member and a die facing the intermediatemember via the reinforcing fiber substrate.

As the above-described intermediate member, a perforated plate or resinfilm provided with a plurality of through holes can be used. In thiscase, a structure can be employed wherein a groove for a resin path isprovided on a die facing the intermediate member. Further, a structurecan also be employed wherein a gap is formed between the intermediatemember and a die facing the intermediate member, and the gap is set in arange of 1 to 10 mm.

Further, a structure can be employed wherein a core material islaminated to the reinforcing fiber substrate, and typically, a sandwichstructure can be employed wherein a core material is nipped withreinforcing fiber substrates from both sides.

Further, to improve the sealability at a position of parting surfaces ofdies of the mold, particularly, to improve the sealability at a resininjection or discharge portion to shorten the cycle time of the RTMmolding, a structure can be employed wherein a tube for resin injectionand/or a tube for resin discharge is provided being nipped betweenparting surfaces of dies, and portions between the tube and the dies aresealed with an elastic material (an elastic material for seal).

In the above-described structure for improvement of sealability, astructure can be employed wherein an end portion of an O-ring forsealing the cavity of the mold at positions of parting surfaces of diesis incorporated into the elastic material for seal.

Further, to discharge bubbles due to evaporation of gas dissolved in theresin which is generated during resin injection or residual fine bubblesin corner portions of the mold, a structure can be employed wherein,while the resin is injected into the mold at a pressurized condition,gas and excessive resin in the mold are discharged intermittently.

In this structure, when a resin pressure in the mold of resinpressurized and injected is referred to as Pm and a resin dischargepressure at an injection port for injecting resin is referred to as Pi,a flow rate of resin flowing into the mold can be controlled byselective control between conditions of Pm=Pi and Pm<Pi. Further, theflow rate of resin flowing into the mold can also be controlled byadjustment of a diameter of a discharge port for discharging resin. Theadjustment of the diameter of the discharge port and a timing for theadjustment may be stored in memory, and based on the stored information,the flow rate of resin flowing into the mold may be automaticallycontrolled.

Further, a structure can be employed wherein, when resin is injectedinto the cavity of the mold at a pressurized condition, a ratio of aflow rate of the resin per a unit time (Q:cc/min.) to a projected areaof the cavity (S:m²) (Q/S:cc/min.·m²) is in a range of 50<Q/S<600.

In this case, a structure can also be employed wherein the product ofthe ratio (Q/S:cc/min.·m²) and a pressurizing force of resin (P:MPa)((Q/S)×P:ccMPa/min.·m²) is in a range of 20≦(Q/S)×P≦400.

Further, a structure wherein a pressurizing force of the resin is in arange of 0.2 to 0.8 MPa, and a structure wherein the resin is cured for3 to 30 minutes at a constant heating temperature in a range of 60 to160° C., can be employed.

The above-described RTM molding method and device according to the firstembodiment employ the following basic concept. Namely, any way, thenumber of the resin injection ports is increased, and a resin flowingregion per one injection port is made small. Then, before the resin isimpregnated into the reinforcing fiber substrate, the resin is onceflown on the surface of the substrate and stored there, and a pressureis applied to the resin and the resin is flown and impregnated at a timeover the entire area. At that time, the substantial resin flow iscontrolled at a range corresponding to the thickness of the substrate.Namely, the resin is flown in a surface direction over a sufficientlywide area beforehand, and from there, the resin is flown and impregnatedat a time in the thickness direction of the substrate. Therefore, theresin is injected into the substrate from the entire area (not from thecircumference), and the resin is impregnated into the substrate veryquickly. The resin discharge is preferably carried out from thecircumference (as the case may be, from the entire circumference).

To carry out such a resin flow operation, in the above-described RTMmolding method and device, an intermediate member forming resin paths(for example, an intermediate plate for resin injection multi-port) isdisposed between dies, for example, between one-side die (for example,an upper die) and the other-side die (for example, a lower die), and theresin is injected to the reinforcing fiber substrate from a plurality ofpositions via the intermediate member almost simultaneously. Forexample, the resin is flown to the reinforcing fiber substrate almostsimultaneously from a plurality of injection ports provided on theintermediate member, and the resin is flown almost uniformly over theentire area of the substrate.

Further, a structure may also be employed wherein an intermediate platewith a small opening area for injection (such as a perforated plate or aperforated film having a great resistance against resin flow) isprovided as the intermediate member between the reinforcing fibersubstrate and the upper die (one-side die), a fine gap (for example, agap in the above-described range of 1 to 10 mm) is maintained betweenthe intermediate plate and the upper die, and the resin is flown intothe gap. Because of the small flow resistance, before the resin flowsfrom the holes of the intermediate plate, the resin expands over asufficiently wide area, the resin is stored, and the resin is injectedin the direction toward the reinforcing fiber substrate through thethrough holes substantially at a time. Therefore, even in this case, theresin can be injected from a plurality of positions almostsimultaneously and uniformly.

Further, we provide an RTM molding method wherein, after resin isimpregnated into the reinforcing fiber substrate by injecting the resinfrom a resin injection line toward a resin discharge line, which aredisposed on an outer circumference of the cavity, the resin is heatedand cured, and the resin injection line is divided into a plurality ofparts (method according to a second embodiment).

Further, we provide an RTM molding device wherein, after resin isimpregnated into the reinforcing fiber substrate by injecting the resinfrom a resin injection line toward a resin discharge line, which aredisposed on an outer circumference of the cavity, the resin is heatedand cured, and the resin injection line is divided into a plurality ofparts (device according to a second embodiment).

In the RTM molding method and device according to the second embodiment,it is preferred that the above-described resin injection line and resindischarge line are formed substantially over the entire range of theouter circumference of the cavity. Further, it is preferred that, withrespect to the above-described resin injection line and resin dischargeline, the length of the resin injection line is two times or more thelength of the resin discharge line.

Such a resin injection line and/or such a resin discharge line can beformed from a groove processed on the mold. In a case where the moldcomprises an upper die and a lower die, it is preferred that the grooveis all processed on the lower die.

Further, the resin discharge line can be also divided into a pluralityof parts.

It is preferred that resin injection from the resin injection linedivided into a plurality of parts is carried out in order from a resininjection line part which is substantially more distant from the resindischarge line. Further, resin injection can be carried out also fromthe resin discharge line by switching the resin discharge line to aresin injection line after a predetermined period of time.

Further, also in the RTM molding method and device according to thesecond embodiment, a structure can be employed wherein a core materialis laminated to the reinforcing fiber substrate, and typically, asandwich structure can be employed wherein a core material is nippedwith reinforcing fiber substrates from both sides.

Further, to improve the sealability at a position of parting surfaces ofdies of the mold, particularly, to improve the sealability at a resininjection or discharge portion to shorten the cycle time of the RTMmolding, a structure can be employed wherein a tube for resin injectionand/or a tube for resin discharge is provided being nipped betweenparting surfaces of dies, and portions between the tube and the dies aresealed with an elastic material (an elastic material for seal).

In the above-described structure for improvement of sealability, astructure can be employed wherein an end portion of an O-ring forsealing the cavity of the mold at positions of parting surfaces of diesis incorporated into the elastic material for seal.

Further, to discharge bubbles due to evaporation of gas dissolved in theresin which is generated during resin injection or residual fine bubblesin corner portions of the mold, a structure can be employed wherein,while the resin is injected into the mold at a pressurized condition,gas and excessive resin in the mold are discharged intermittently.

In this structure, when a resin pressure in the mold of resinpressurized and injected is referred to as Pm and a resin dischargepressure at an injection port for injecting resin is referred to as Pi,a flow rate of resin flowing into the mold can be controlled byselective control between conditions of Pm=Pi and Pm<Pi. Further, theflow rate of resin flowing into the mold can also be controlled byadjustment of a diameter of a discharge port for discharging resin. Theadjustment of the diameter of the discharge port and a timing for theadjustment may be stored in memory, and based on the stored information,the flow rate of resin flowing into the mold may be automaticallycontrolled.

Further, a structure can be employed wherein, when resin is injectedinto the cavity of the mold at a pressurized condition, a ratio of aflow rate of the resin per a unit time (Q:cc/min.) to a projected areaof the cavity (S:m²) (Q/S:cc/min.·m²) is in a range of 50<Q/S<600.

In this case, a structure can also be employed wherein the product ofthe ratio (Q/S:cc/min.·m²) and a pressurizing force of resin (P:MPa)((Q/S)×P:ccMPa/min.·m²) is in a range of 20≦(Q/S)×P≦400.

Further, a structure wherein a pressurizing force of the resin is in arange of 0.2 to 0.8 MPa, and a structure wherein the resin is cured for3 to 30 minutes at a constant heating temperature in a range of 60 to160° C., can be employed.

Further, to achieve the aforementioned third object, we provide an RTMmolding method wherein at least one surface layer of the reinforcingfiber substrate comprises a continuous fiber layer, and a layerpositioned immediately under the surface layer comprises a random matlayer (method according to a third embodiment).

Since the random mat layer is random in fiber orientation and low inweight, the resistance against resin flow is low, and by providing thisrandom mat layer, it becomes possible to form a resin flow path in whichresin can flow relatively easily. By disposing this random mat layerimmediately under the surface layer of the continuous fiber substratewhich is at least one surface layer, when resin is injected, a goodresin flow can be formed near the surface layer, in particular, in adirection along the surface of the surface layer, and a portion improperin resin impregnation, which may become void, can be prevented frombeing generated, thereby improving the surface of the molded product.

In the RTM molding method according to this third embodiment, it ispreferred that the surface layer is formed from three or less continuousfiber layers. If the continuous fiber substrate is too thick, becausethere is a fear that resin is hard to reach the random mat layer throughthe substrate, or that the resin having flown well in the random matlayer is hard to be impregnated into the continuous fiber substrate ofthe surface layer, the lamination form of the continuous fiber substrateof the surface layer is preferably a form of three or less layers.

Further, it is preferred that the total weight of the continuous fiberlayer forming the surface layer is 700 g/m² or less, and from theviewpoint of surface design quality, preferably it is formed as a wovenfabric with a weave structure such as a plain weave, a twill weave orsatin weave. Further, although bubbles causing pinholes are likely tostay in the weave textures of these woven fabrics, as described above,occurrence of pinholes can be prevented by disposing a random mat layerimmediately under the surface substrate and discharging bubbles. Thissurface layer can be made of, for example, a carbon fiber woven fabric.As the reinforcing fibers, carbon fibers, glass fibers, aramide fibers,metal fibers, boron fibers, alumina fibers, silicon carbidehigh-strength synthetic fibers, etc. can be used, and in particular,carbon fibers and glass fibers are preferred. Among these, it ispreferred that the reinforcing fibers of the above-described surfacelayer are formed as a carbon fiber woven fabric.

As the total weight of the above-described random mat layer, because therandom mat layer is disposed mainly for the purpose of forming a resinflow path with a small resistance at the time of resin flow and resinimpregnation, the total weight is preferably 150 g/m² or less which islower than that of the surface substrate or the reinforcing fibersubstrate. This random mat layer contributes to improve the surfacequality by decreasing the flow resistance of matrix resin lower thanthat of the reinforcing fiber layer and greatly improving theflowability and the impregnation property of the resin, therebypreventing occurrence of voids and pinholes. Therefore, as long as thispurpose can be achieved, it is not preferred that the random mat layer,which almost does not function as reinforcing fibers, is too much, fromthe viewpoint of maintaining the mechanical properties of FRP such asstrength and rigidity, and as described above, it is preferred that thetotal weight is 150 g/m² or less.

Further, although carbon fibers or aramide fibers may be used for therandom mat layer, glass fibers that are relatively cheap can be used forthis layer, and the glass fibers are more preferable.

Further, also in the RTM molding method according to this thirdembodiment, a structure can be employed wherein a core material islaminated to the reinforcing fiber substrate, and typically, a sandwichstructure can be employed wherein a core material is nipped withreinforcing fiber substrates from both sides.

By such an RTM molding method according to this third embodiment, theinjected resin can be easily and surely delivered over the entire rangeof a desirable area in the resin injection step, voids and pinholes canbe prevented from being generated on the surface, in particular, on thedesign surface side, thereby obtaining a fiber reinforced resin with animproved surface quality. This RTM molding method according to the thirdembodiment can be used by combining with the RTM molding methodaccording to the aforementioned second embodiment, and in such a case,the advantage due to the random mat layer can be exhibited better.

In the RTM molding method and device, since adequate divided areas areassumed and the injected resin can be delivered enough to the respectivedivided areas and can be impregnated well into the respective dividedareas even if a reinforcing fiber substrate with a relatively large areais used, the molding process from resin injection to impregnation andcuring can be carried out at a high speed without generatingnon-resin-flowing areas, thereby achieving shortening of the moldingtime and increase of production speed and production amount, andreducing the production cost. Further, the resin can be impregnated at adesirable state over the entire area, thereby improving the surfacequality of the molded product.

In particular, in the RTM molding method and device according to thefirst embodiment, since the resin is flown in advance so as to be spreadto a sufficiently wide area via the intermediate member and thereafterthe resin is injected into the reinforcing fiber substrate from aplurality of positions almost simultaneously and uniformly, even as fora relatively large three-dimensional configuration, the molding can becarried out at a high speed without generating non-resin-flowing areas.As a result, the molding time is greatly shortened, it becomes possibleto increase the production speed and the production amount, and itbecomes, possible to reduce the production cost by increasing theproduction amount per one mold. Further, even as for a large-sizedproduct to be molded, it becomes possible to easily prevent generationof resin non-impregnated portions, thereby improving the quality of themolded product.

Further, in the RTM molding method and device according to the secondembodiment, a relatively large FRP product can be molded efficiently andstably in a short period of time without occurrence of defects such asvoids, which has been difficult by a conventional RTM molding method.Namely, mass production with a high-cycle becomes possible.

Furthermore, in the RTM molding method according to the thirdembodiment, by disposing the random mat layer with a weight lower thanthat of the layer of surface layer or the layer of the reinforcing fibersubstrate immediately under the continuous fiber substrate of at leastone surface layer, when the resin is injected and impregnated into thereinforcing fiber substrate, resin flow paths with a small flowresistance and easy to flow resin are formed, and the injected resin iswell delivered up to the detailed portions because the fiber orientationis random, thereby preventing occurrence of defects such as voids andpinholes ascribed to resin non-impregnated portions. In particular, by acondition where the random mat layer is disposed immediately under thesurface layer, it can be efficiently prevented that such defects aregenerated on the surface of the molded product, and the surface qualityof the molded product, particularly, the quality of the design surface,can be effectively improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a device used in an RTMmolding method according to a first embodiment.

FIG. 2A is a plan view of an upper die of the device depicted in FIG. 1,and FIG. 2B is an elevational view thereof.

FIG. 3A is a plan view of an intermediate member of the device depictedin FIG. 1, and FIG. 3B is a sectional view as viewed along the line C-Cof FIG. 3A.

FIG. 4A is a plan view of a lower die of the device depicted in FIG. 1,and FIG. 4B is a sectional view as viewed along the line C-C of FIG. 4A.

FIG. 5 is a sectional view of a device used in an RTM molding methodaccording to another embodiment different from the first embodiment.

FIG. 6 is a bottom view of an upper die of the device depicted in FIG.5.

FIG. 7 is a plan view of a lower die of the device depicted in FIG. 5.

FIG. 8 is a perspective view of a mold used in RTM molding method anddevice according to a second embodiment.

FIG. 9 is a plan view of a lower die of the mold depicted in FIG. 8.

FIG. 10 is a vertical sectional view of the lower die depicted in FIG.9.

FIG. 11 is a schematic diagram of the whole of an RTM molding systemusing the RTM molding method and device according to the secondembodiment.

FIG. 12 shows graphs of characteristics of a resin used in our examples.

FIG. 13 is a partial sectional view showing a structure of a preformsubstrate of fiber reinforced resin molded by an RTM molding methodaccording to a third embodiment.

FIG. 14 is a partial sectional view showing an aspect at the time ofinjecting and impregnating resin into the substrate depicted in FIG. 13.

FIG. 15 is a partial sectional view showing a structure of a preformsubstrate of fiber reinforced resin molded by an RTM molding methodaccording to another embodiment different from the third embodiment.

FIG. 16 is a partial sectional view showing an aspect at the time ofinjecting and impregnating resin into the substrate depicted in FIG. 15.

FIG. 17A is a partial sectional view of the surface layer substrate ofthe preform substrate depicted in FIG. 13, and FIG. 17B is a plan viewthereof.

FIGS. 18A to 18C are schematic diagrams showing a molding method capableof being used in the third embodiment.

FIG. 19 is a partial sectional view showing a structure of a fiberreinforced resin according to another embodiment different from theembodiment depicted in FIG. 13.

FIG. 20 is a schematic exploded perspective view of a mold showing anexample of a structure for improving sealability in RTM molding methodand device.

FIG. 21 is a vertical sectional view of a mold showing another exampleof a structure for improving sealability.

FIG. 22 is a perspective view of a tube portion for resin injection •discharge used for parting surfaces of dies of a mold.

FIGS. 23A to 23F are schematic diagrams showing various examples ofsealing forms for tube portions for resin injection • discharge disposedon parting surfaces of dies of molds.

EXPLANATION OF SYMBOLS

-   -   1, 20: mold    -   2, 21: upper die    -   3, 24: intermediate member    -   4, 22: lower die    -   5: groove for resin injection path    -   6, 24 a: through hole    -   8, 26: resin injection member    -   9, 23: reinforcing fiber substrate    -   11, 27: resin discharge member    -   25: gap (clearance)    -   41: RTM mold    -   42: upper die    -   43: lower die    -   44: preform substrate (reinforcing fiber substrate)    -   45: mold sealing material    -   46, 47, 48: resin injection tube    -   46 a, 47 a, 48 a: rubber member for seal    -   46 b, 47 b, 48 b: resin injection valve    -   46 c, 47 c, 48 c: resin injection runner    -   46 d, 47 d, 48 d: resin injection film gate    -   49: resin discharge tube    -   49 a: rubber member for seal    -   49 b: resin discharge valve    -   49 c: resin discharge runner    -   49 d: resin discharge film gate    -   50: cavity    -   51: hole for pin    -   52: pin    -   54: RTM molding system    -   55: mold lifting device    -   56: hydraulic device for mold lifting    -   57: resin injection device    -   58: vacuum pump    -   59: resin trap    -   60: temperature controller    -   61 a: main ingredient tank    -   61 b: curing agent tank    -   62: pressurization device    -   63: mixing unit    -   64: divergent tube    -   65: resin injection path    -   66: hydraulic cylinder    -   67: discharge path    -   68: hydraulic pump    -   71, 76, 100: fiber reinforced resin    -   72, 72 a, 72 b: surface layer substrate    -   73, 73 a, 73 b: random mat layer    -   74, 74 a, 74 b: reinforcing fiber substrate forming a        reinforcing layer    -   75 a, 75 b, 75 c, 75 d: stream line of resin flow    -   75, 77 a, 77 b: resin    -   78, 79, 82: bubble    -   83: upper die    -   84: lower die    -   85: resin injection port    -   86: suction port    -   87: preform substrate    -   88: runner for resin injection    -   89: runner for suction    -   90: seal groove    -   91: resin tank    -   92, 95: valve    -   93: resin injection route    -   94: vacuum pump    -   96: suction route    -   97: molded product    -   101: core material    -   111, 131, 151: upper die    -   112, 132, 152: lower die    -   113, 133: cavity    -   114, 138 runner for resin injection    -   115, 139: runner for resin discharge    -   116, 134: tube for resin injection    -   117, 135: tube for resin discharge    -   118, 119, 136, 137, 153: elastic material for seal    -   121, 154: O-ring    -   122: reinforcing fiber substrate    -   123: reinforcing fiber preform material    -   124: core material    -   125: reinforcing fiber substrate    -   126, 127: gate

DETAILED DESCRIPTION

Hereinafter, desirable embodiments will be explained referring tofigures.

First, as the reinforcing fibers, carbon fibers, glass fibers, aramidefibers, metal fibers, boron fibers, alumina fibers, silicon carbidehigh-strength synthetic fibers, etc. can be used, and particularlycarbon fibers are preferable. The form of the reinforcing fibersubstrate is not particularly limited, a unidirectional sheet or a wovenfabric can be employed, usually a plurality of these are stacked to forma reinforcing fiber substrate, and it is used as a formation of apreform given with a predetermined form beforehand in accordance withrequirements.

As the resin used in the RTM molding method and device, a thermosettingresin, which is low in viscosity and easy to be impregnated intoreinforcing fibers, or a monomer for RIM (Resin Injection Molding)forming a thermoplastic resin, etc., is suitable. As the thermosettingresin, for example, an epoxy resin, an unsaturated polyester resin, apolyvinylester resin, a phenolic resin, a guanamine resin, a polyimideresin such as bismaleimide • triazine resin, a furan resin, apolyurethane resin, a polydiarylphthalate resin, further, a melamineresin, a urea resin, an amino resin, etc. can be raised.

Further, a polyamide such as nylon 6, nylon 66 or nylon 11, or acopolymerized polyamide of these polyamides, a polyester such aspolyethylene terephthalate or polybutylene terephthalate, or acopolymerized polyester of these polyesters, further, a polycarbonate, apolyamideimide, a polyphenylene sulfide, a polyphenylene oxide, apolysulfone, a polyethersulfone, a polyetheretherketone, apolyetherimide, a polyolefine, etc., and furthermore, a thermoplasticelastomer represented by a polyester elastomer, polyamide elastomer,etc. can be raised.

Further, a resin prepared by blending a plurality of components selectedfrom the group of the above-described thermosetting resins,thermoplastic resins and rubbers also can be used.

As a preferable resin, an epoxy resin can be raised, from the viewpointof suppressing a thermal shrinkage at the time of molding whichinfluences a design quality of an outer panel for vehicles.

In a general epoxy resin for a composite material, as its mainingredient, bisphenol A-type epoxy resin, phenol novolak-type epoxyresin or glycidyl amine-type epoxy resin is used. On the other hand, asthe curing agent, a curing agent prepared by combining dicyanediamidewith dichlorophenyldimethyl urea is suitably used from the viewpoint ofits good balance between workability and properties. However, it is notparticularly limited, and diaminophenylsulfone, aromatic diamine, acidanhydride polyamide, etc. also can be used. Further, the ratio of theresin to the above-described reinforcing fibers is preferably in a rangeof 20:80 to 70:30 in weight ratio, from the viewpoint of maintaining anappropriate rigidity as an outer panel. In particular, an epoxy resin ora modified epoxy resin compounded with a thermoplastic resin, a rubbercomponent, etc., a nylon resin, or a dicyclopentadiene, is moresuitable, from the viewpoint of decreasing thermal shrinkage of an FRPstructural material and suppressing occurrence of cracks.

Further, this disclosure can be applied to molding of a fiber reinforcedresin structural material having a lamination structure of a fiberreinforced resin and a core material. For example, a sandwich structurein which fiber reinforced resin layers are disposed on both sides of acore material can be raised. It is possible to use an elastic material,a foamed material or a honeycomb material as the core material, and afoamed material and a honeycomb material are preferable for lighteningin weight. The kind of the foamed material is not particularly limited,and for example, a foamed material of a polymer such as polyurethane,acrylic, polystyrene, polyimide, vinyl chloride or phenol can be used.The material of the honeycomb material is not particularly limited, andfor example, an aluminum alloy, a paper, an aramide paper, etc. can beused.

FIGS. 1 to 4 show RTM molding method and device according to a firstembodiment. In FIG. 1, a mold 1 comprises a plurality of dies, and inthis embodiment, it has an upper die 2 made of a steel as a one-side dieand a lower die 4 made of the same material as the other-side die andhas an intermediate plate 3 made of a resin (for example, polyethylene)as an intermediate member. Resin injection paths and injection ports areformed by these upper die 2 and intermediate plate 3. Grooves 5 forresin injection path, which communicate with a resin injection member 8,are processed on intermediate plate 3, and a through hole 6 forinjection port is processed at an end portion of each groove 6. Theresin injection member 8 is formed from a metal pipe of a resin tube,and it is sealed relative to a metal die forming upper die 2 andintermediate plate 3 by a seal material 10 a made of an elastic materialsuch as a rubber. The circumference of upper die 2 and intermediateplate 3 is sealed by an O-ring 7, and the O-ring 7 is combined with sealmaterial 10 a. On four corners of upper die 2, guides 13 are providedfor connecting the upper die 2 to intermediate plate 3 and lower die 4.

A reinforcing fiber substrate 9 is disposed on the cavity portion oflower die 4, and a groove 12 (runner) for resin discharge is processedon the outer circumference side of the substrate 9. An excessive resinis discharged to outside of the mold from a resin discharge tube 11inserted into a part of groove 12. An O-ring 14 for seal is disposed onthe circumference of the groove 12, and the O-ring 14 is combined with aseal material 10 b made of an elastic material and the like and providedfor sealing between tube 11 and die 4.

FIG. 2 shows upper die 2, FIG. 2A is a plan view thereof, and FIG. 2B isan elevational view thereof. A resin injection path 15 is formed onupper die 2, and the upper half of resin injection member 8 is stored inthe entrance of the path 15.

FIG. 3 shows intermediate plate 3, FIG. 3A is a plan view thereof, andFIG. 3B is a sectional view thereof as viewed along line C-C of FIG. 3A.The dimension of intermediate plate 3 in this example is 1800 mm inwidth, 2000 mm in length and 12 mm in thickness. Grooves 5 for resininjection path, which communicate with resin injection member 8 made ofa metal pipe or a resin tube, are processed on intermediate plate 3 soas to extend radially, and through holes 6 for injection ports, eachhaving a diameter of 5 mm, are processed on an intermediate portion andend portions the grooves 5. In this example, the width of the groove is5 mm the depth is 4 mm, and the length of each path radially extendingis 540 mm. The circumference is sealed by O-ring 7, and the O-ring 7 iscombined with the above-described elastic material 10 a.

FIG. 4 shows lower die 4, FIG. 4A is a plan view thereof, and FIG. 4B isa sectional view thereof as viewed along line C-C of FIG. 4A.Reinforcing fiber substrate 9 (for example, “TORAYCA” T300 woven fabricof plain weave CO6644B (weight: 300 g/m²), 6 ply) is laid up on thecentral cavity portion of the molding surface. On the outercircumference side of the substrate, groove 12 for resin discharge afterresin impregnation (runner: the dimension is 12 mm in width and 5 mm indepth.) is processed. An excessive resin is discharged to outside of themold from resin discharge tube 11 having an outer diameter 12 mm and aninner diameter of 12 mm which is inserted into a part of the groove 12.

In the molding using upper and lower dies 2, 4 and intermediate plate 3thus constructed, because a plurality of resin paths are formed by theintermediate plate 3, the resin injected from resin injection member 8,first, flows quickly in a direction along the surface of theintermediate plate 3, and the resin is delivered over a wide area. Then,because the resin is injected into reinforcing fiber substrate 9substantially almost simultaneously from a plurality of positionsthrough a plurality of through holes 6 provided appropriately, the resinis being well impregnated quickly into the reinforcing fiber substrate 9over a wide area of the substrate 9. Namely, because the flow resistanceof through holes 6 is higher than that of the resin paths, the injectedresin is once stored on the surface of intermediate plate 3, and theresin is then impregnated from there into reinforcing fiber substrate 9at a time through a plurality of through holes 6. As the result of anactual molding using an epoxy resin at a mold temperature of 90° C.,occurrence of resin non-delivered portion can be prevented, and the timefor resin injection and impregnation is greatly shortened to 1/10 orless of a conventional time, thereby achieving a high-speed molding.

FIGS. 5 to 7 show RTM molding method and device according to anotherembodiment different from the above-described first embodiment. In FIG.5, an intermediate member 24 consisting of a perforated plate an aperforated film (in this embodiment, a perforated plate) is set betweenan upper die 21 and a lower die 22 of a mold 20. Grooves 36 a, 36 b(FIG. 6) for resin paths are processed on upper die 21 so as to extendover the entire area. A clearance 25, a fine clearance 25 of about 1 mmin this embodiment, is formed between perforated plate 24 and upper die21. Further, a more efficient resin flow and impregnation becomespossible if the positions of holes of a perforated plate or a perforatedfilm coincide with the positions of the grooves formed on the upper die.Most of the resin flown from a resin injection member 26 sealed with aseal member 28 (for example, a rubber block) flows to theabove-described clearance 25, and is filled in the space of theclearance 25. On perforated plate 24, fine through holes 24 a (diameter:about 0.5 to about 3.5 mm) are opened over the entire area at a pitch of3 to 8 mm. Therefore, the flow resistance of the resin of the perforatedplate 24 is much higher than that in the resin flow to theabove-described clearance 25. A reinforcing fiber substrate 23 is set ina cavity 31, upper die 21 is clamped, and vacuum suction is carried outthrough a discharge member 27 sealed with a seal member 29. The resinhaving been charged in the above-described clearance 25 is pressurized,and the resin is injected at a pressurized condition at a time over theentire area from through holes 24 a of perforated plate 24. An excessiveresin after impregnation flows a film gate/runner provided on thecircumference of cavity 31, and it is discharged from discharge tube 27to outside. After impregnation over the entire area, the discharge tube27 is closed, and while the resin pressure is maintained, heating/curingis carried out. In die opening, upper die 21 is lifted up, a moldedproduct is taken out together with perforated plate 24 from lower die22, and the molded product is separated from the perforated plate 24. Ina case where the separation from perforated plate 24 or a postprocessing for a molded product adhered with resin projections istroublesome, it had better to dispose a cloth for release (a wovenfabric made of polypropylene or polyethylene: also called a peel ply)between perforated plate 24 and reinforcing fiber substrate 23beforehand. Further, as the case may be, only a cloth for release may bedisposed without disposing perforated plate 24.

FIG. 6 shows upper die 21, and thereon, grooves 36 a, 36 b for resinpaths for distributing the resin to the molding surface side over itsentire area are processed. As an example, a main path (width: 8 mm,depth: 5 mm) is present, and on both sides thereof, sub paths (width: 3mm, depth: 3 mm) are processed almost up to the end at a pitch of 10 mm.Further, grooves 32, 33 are processed for disposing seal members 28, 29for sealing between resin injection tube 26 or resin discharge tube 27and the die.

FIG. 7 shows lower die 22, and thereon, cavity 31 for molding isprocessed on the die almost over the entire surface. A film gate andrunner 30 connected to cavity 31 are processed on the resin dischargeside. Grooves 34, 35 for disposing seal members 28, 29 for sealingbetween resin injection tube 26 or resin discharge tube 27 and the die,and groove 37 for O-ring for seal, are processed on the die at positionscorresponding to those of upper die 21.

In the molding using thus constructed upper and lower dies 21, 22 andperforated plate 24 provided as an intermediate member, the resin isflown quickly in clearance 25 in the direction along the surface ofperforated plate 24, and the resin is filled over a wide area. Becausethe resin is then injected into reinforcing fiber substrate 23 from aplurality of positions substantially almost simultaneously through manythrough holes 24 a provided on perforated plate 24, the resin is wellimpregnated quickly into the reinforcing fiber substrate 23 over thewide area. Therefore, also in this embodiment, occurrence of resinnon-delivered portion can be prevented, the time for resin injection andimpregnation can be greatly shortened, and a high-speed molding can beachieved.

Example 1

In the above-described respective embodiments, when molding was carriedout setting the size of a mold at 1500 mm×1200 mm×depth 3 mm at themolding surface (the cavity surface), using a laminate of 8 plies of“TORAYCA” T700 cloth BT70-30 (300 g/m²) produced by Toray Industries,Inc. as the reinforcing fiber substrate, and using a high-speed curingtype epoxy resin (main ingredient: “Epicoat” 828 (an epoxy resinproduced by Yuka Shell Epoxy Corporation), curing agent: blend TR-C35H(an imidazole derivative) produced by Toray Industries, Inc.) as theresin, in spite of a relatively large molded product, a good and quickmolding could be carried out. The time for completing the impregnationof the resin into the substrate was 5 minutes or less at a resininjection pressure of 0.7 MPa, and could be shortened down to ⅕- 1/10 orless of a conventional method.

FIGS. 8 to 12 show RTM molding method and device according to the secondembodiment. FIG. 11 is a schematic diagram showing an example of amolding system 54 using an RTM molding device. A mold 41 for RTM moldingcomprises an upper die 42 and a lower die 43, and the upper die 42 isattached to a mold lifting device 55 lifted by a hydraulic device formold lifting 56 with a hydraulic pump 68 and a hydraulic cylinder 66. Areinforcing fiber substrate directly, or a preform substrate 44 (areinforcing fiber substrate) given with a product shape beforehand so asto be easily placed in the mold, is disposed on the lower die 43, andthen, the upper die 42 is closed. As the material of the mold, an FRP, acast steel, a structural carbon steel, an aluminum alloy, a zinc alloy,a nickel electrocast material, and a copper electrocast material can beraised. For mass production, a structural carbon steel is preferred fromthe viewpoint of rigidity, thermal resistance and workability.

A plurality of resin injection tubes 46, 47, 48 connected to a resininjection runner and a single discharge tube 49 connected to a dischargerunner are provided to mold 41. The respective resin injection tubes 46,47, 48 and discharge tube 49 are connected to resin injection path 65and discharge path 67 via respective injection valves 46 b, 47 b, 48 band discharge valve 49 b. In a resin injection device 57, the mainingredient is stored in main ingredient tank 61 a and the curing agentis stored in curing agent tank 61 b, respectively, and each tank has amechanism for heating and vacuum degassing. At the time of resininjection, the resin is pushed out from the respective tanks toward theresin injection path 65 by a pressurizing device 62. The pressurizingdevice 62 uses syringe pumps 62 a, 62 b as an example, and for a resincured by mixing of two liquids, it is preferred to ensure thequantitative property by pushing out the syringe pumps simultaneously.The pushed-out main ingredient and curing agent are mixed in a mixingunit 63, and the mixture reaches the resin injection path 65. Dischargepath 67 is connected to a resin trap 59 in order to prevent a resin flowto a vacuum pump 58.

Although the number and the positions of the resin injection tubes aredifferent in accordance with the shape or the dimension of the mold orthe number of molded products to be molded simultaneously in a singlemold, in order to prevent the injection operation from becomingtroublesome by increase of the number of the positions for connectingthe injection path 56, which extends from resin injection device 57, toresin injection tubes 46, 47, 48, the number of the injection tubes ispreferably as few as possible. However, to mold a relatively largeproduct at a high speed, it is possible to flow and impregnate the resinefficiently at a speed of several times relative to that in resininjection by a single injection tube, by using a plurality of resininjection tubes and carrying out the resin injection simultaneously orin order.

FIG. 9 is a plan view of an RTM mold for a high-speed molding of a flatplate with rounds at its four corners, in particular, a plan view oflower die 43. As shown in FIG. 8, upper die 42 and lower die 43 arealigned in position with each other by inserting pins 52 provided on theside of upper die 42 into holes 51 for the pins provided on the side oflower die 43, and the dies are clamped at a closed condition interposinga mold seal 45 therebetween. FIG. 10 shows a vertical section of themold depicted in FIG. 9. As explained referring to FIG. 9, in aconventional RTM molding method as a method for molding a flat plate,the resin is injected at a pressurized condition from injection tube 46communicating with resin injection runner 46 c and resin injection filmgate 46 d which form a resin injection line present on one side of outersides of cavity 50 for molding, the resin flows toward discharge filmgate 49 d and discharge runner 49 c which form a resin discharge linecommunicating with discharge tube 49 provided on the opposite positionand present on another side of the outer sides of the cavity 50, and isimpregnated into the reinforcing fiber substrate. Namely, it is a methodfor flowing the pressurized resin from the resin injection line to thereinforcing fiber substrate in the cavity of the mold and impregnatingthe resin into the substrate, from the single resin injection line whichis formed at a single side of the outer sides of the cavity 50 of themold (formed from resin injection runner 46 c and resin injection filmgate 46 d communicating with resin injection tube 46), toward the singleresin discharge line which is formed at another single side of the outersides of the cavity of the mold (formed from resin discharge film gate49 d and resin discharge runner 49 c communicating with resin dischargetube 49).

In this method, although a relatively short-time molding can be carriedout and a mass production is possible in a case of molding a relativelysmall molded product, that is, in a case of a molded product thedistance from the resin injection line to the discharge line of which issmall, in a case of a large molded product, that is, in a case of amolded product the distance from the resin injection line to thedischarge line of which is great, because the resin flow is damped at acondition of a high-order function, the time for the resin flow becomeslong, and as the case may be, there is a case where the impregnation isnot completed by the time of resin gelation. In such a case, although amethod for injecting the resin at a high speed by using a low-viscosityresin or by increasing the pressure of the resin is employed, thereinforcing fibers may be disturbed by the pressure for the resin flow,or a limit for impregnation over the entire area of the product to bemolded may exist depending upon the size or the shape of the product tobe molded.

In a case where a high-speed molding and a mass production are difficultby the conventional RTM molding method because the product to be moldedis large as described above, as shown in FIG. 9, the problem can besolved by providing the resin injection line not at a single side of theouter sides of cavity 50 for molding but at a plurality of positions.Namely, by adding resin injection tubes 47, 48 toward resin dischargeline 49 except the conventional resin injection tube 46 as the resininjection line, and injecting the resin simultaneously or in order fromthe resin injection line formed by resin injection runner 46 c and resininjection film gate 46 d, the resin injection line formed by resininjection runner 47 c and resin injection film gate 47 d and the resininjection line formed by resin injection runner 48 c and resin injectionfilm gate 48 d, the problem of the resin flow damped at a condition of ahigh-order function can be solved. Namely, it is to provide the resininjection line and the resin discharge line so as to extendsubstantially over the entire area of the outer circumference of theproduct to be molded (that is, the whole of the reinforcing fibersubstrate). A particularly effective method is to provide the resininjection line over the half or more of the outer circumference, andmore desirably, if the resin injection line is disposed so as to becometwo times or more of the resin discharge line, an extremely efficientand high-speed molding becomes possible. Symbols 46 a, 47 a, 48 a 49 ain FIG. 9 indicate rubber members for seal, respectively.

It is necessary to decide depending upon the size and shape of a moldedproduct as to whether the resin injection from resin injection tubes 47,48 supplementing the resin injection from resin injection tube 46 shouldbe carried out or not and as to the injection timing thereof. Further,in such a case, because the resin supplemented from the resin injectiontubes 47, 48 is likely to flow easily to the side portion rather thanthe central portion of the substrate, there is a case where a correctionbecomes necessary such as making the length of the resin discharge lineshorter than that of one side or changing the position of resindischarge tube 49.

Furthermore, in a case where the product to be molded has a relativelysymmetric shape such as a flat plate shown in FIG. 8 and FIG. 9 or theL/D (a ratio of length to width) is relatively large, for example, theL/D is two times or more, a method is also effective for setting theresin injection line from resin injection tube 46 to a resin dischargeline from the initial stage except resin discharge line 49, andefficiently impregnating the resin by dividing the resin injected fromthe resin injection tubes 47, 48 in the left and right directions.

Further, it is also effective to switch the resin discharge line to theresin injection line at the time when the resin is injected almost overthe entire area of the reinforcing fiber substrate or on the waythereof. Namely, in a case where the resin flowability is bad and theresin does not reach the resin discharge line even if the flowing out ofthe resin into the resin discharge line is waited, by injecting theresin from the resin discharge line, non-impregnation of the resin canbe prevented.

For example, a resin detection sensor for detecting a resin flow stateis disposed in the mold, and in a case such as one where the gelation ofthe resin begins and the flow is stopped before the resin reaches theresin discharge line, the resin injection from the resin discharge lineis effective to prevent non-impregnation.

It is necessary to consider ensuring of an enough flow rate andconformity with the resin (thermal resistance, solvent resistance,pressure tightness, etc.) for the material of resin injection path 65and resin injection tubes 46, 47, 48. Tubes having an inner diameter of5 to 30 mm are used for the injection path and the injection tubes, apressure tightness of 1.0 MPa or more is required to resist the resininjection pressure, and a thermal resistance of 100° C. or higher isrequired to resist the temperature at the time of resin curing. Forthis, for example, a tube of “Teflon” (registered trade mark) having athickness of about 2 mm is suitable. However, except “Teflon”(registered trade mark), a relatively cheap polyethylene tube or nylontube, further, a metal tube made of a steel, aluminum, copper, etc. maybe employed.

Although the number and the position of resin discharge tube 49 aredifferent in accordance with the shape and the dimension of the mold,the number of products to be molded simultaneously in a single mold,etc., the number of resin discharge ports is preferably as few aspossible from the viewpoint of stable resin flow and easy operation forcontrolling the resin flow.

It is necessary to consider ensuring of an enough flow rate andconformity with the resin (thermal resistance, solvent resistance,pressure tightness, etc.) also for the material of resin discharge tubeand the resin discharge path similarly to in the resin injection path65, etc. Although a tube made of a metal such as a steel or an aluminum,or a tube made of a plastic such as polyethylene or “Teflon” (registeredtrade mark), can be raised as the resin discharge path 67, a tube madeof “Teflon” (registered trade mark) having a diameter of 5 to 10 mm anda thickness of 1 to 2 mm is more preferable from the viewpoint ofworkability.

It is possible to open/close injection valves 46 b to 48 b and resindischarge valve 49 b provided for the time of resin injection from resininjection paths 46 to 48 and provided on the way of resin discharge path49 or to change the diameters thereof by nipping the valves directly byan operator with vice grips, etc. Further, it is possible to dispose anactuator at the handle portion of the vice grip for automatic operationor to apply a valve opening/closing device using an electromagneticvalve or an air operation valve instead of the vice grip. Further, it ispreferable to carry out a more accurate opening/closing operation byconnecting this valve opening/closing device to a memory device inputtedwith information of valve opening degree beforehand. Moreover, it isalso possible to control the resin discharge valve 49 b not merely attwo values of opening and closing but to change the diameter of the flowpath (adjustment of opening degree of a ball valve).

For pressurization of resin, if a method of pressurization by a syringepump, etc. is employed, a quantitative property can also be obtained.The resin injection pressure is preferably in a range of 0.1 to 1.0 MPa.Where, the resin injection pressure means the maximum pressurepressurized by pressurization device 62.

When the resin is completely impregnated into the reinforcing fibersubstrate in the mold and the resin has reached up to the resindischarge tube 49 and the resin discharge path 67, the discharge valve49 b is closed, thereafter, for a while the inside of the mold ismaintained at a pressure pressurized by the resin pressurization device62, and after that, the resin injection is finished by closing the resininjection valves 46 b to 48 b. The mold is being heated by a heat mediumcirculation type temperature controller 60, and by this, the resin iscured. As the heat medium, water, steam, mineral oil, etc. can be used.

In the RTM molding carried out by the above-described RTM molding device(RTM molding system) 54, to stably obtain a high-quality FRP moldedproduct excellent in appearance quality without defects such as voidsand having desired mechanical properties, a molding condition from resininjection, impregnation up to curing is very important as well asrationalization of advance preparation such as cutting and lamination ofthe reinforcing fiber substrate, making is as a preform, and lay up intothe mold. In particular, it is necessary to set the productionconditions considered with productivity (efficient production).

For this, it is necessary that the already pointed out “resin injectionpressure,” “molding temperature,” “resin flow rate,” “thermal propertyof resin,” etc. are set at values corresponding to the molding dimensionsufficiently in consideration of the properties of the reactive resin.In particular, because a reactive resin material, which is gelated in ashort period of time and quickly cured although it has a goodflowability, is employed in consideration of efficiency of production, ahigh-speed flow and impregnation becomes necessary.

However, if the resin pressure is increased and the resin injection iscarried out at an increased flow rate, as aforementioned, disturbance ofthe substrate and voids and pits on the surface are liable to occur.Therefore, because there occurs a problem of the aforementionedappearance quality merely by increasing the flow rate, it is necessaryto set a resin flow rate proper for the substrate to be impregnated,namely, a flow rate corresponding to the area of the substrate.

In the RTM molding method and device according to this embodiment,included are not only a usual RTM molding method wherein the moldcomprised upper and lower dies having parting surfaces, while thepressurized resin is flown from the resin injection port, the resin isdischarged together with air in the mold at the resin discharge port,the discharge port is closed at the time of completing the discharge ofair, and the resin in the mold is cured while pressurized, but also anRTM molding method wherein the resin is injected while air in the moldis discharged or after the air is almost discharged by vacuum suction,thereafter, the suction port is closed and the resin is injected at apressurized condition and cured, and further, a vacuum RTM moldingmethod wherein the cavity portion of the mold is covered with a baggingmaterial such as a film at its one surface, after the cavity portion issucked at a vacuum condition, and the resin is injected into the cavityportion by the vacuum pressure and molded.

Example 2

In the RTM molding system 54 according to this embodiment shown in FIG.11, as an example of molding at molding conditions, an example ofmolding of a large flat plate (length of 1600 mm×width of 700 mm×height(thickness) of 2 mm) will be explained. The whole of the RTM mold 41used in this example is shown in FIGS. 8 and 9, and the relationshipbetween the temperature and the viscosity of the resin used for themolding and the property in resin curing degree-time at the moldingtemperature are shown in FIG. 12A and FIG. 12B, respectively. On themolding cavity portion 50 provided on the lower die 43 of the mold 41(length: 2000 mm, width: 1000 mm and height: 350 mm in each of upper die42 and lower die 43) having resin injection tubes 46 to 48 and dischargetube 49, carbon fiber “TORAYCA” cloth (CO6343B: T300B-3K, weight: 192g/m²) is laminated by 8 plies (0/90° oriented substrates: 4 plies, ±45°oriented substrates: 4 plies), a preform substrate 44 given with a plateshape in advance was disposed, and the upper die 42 was closed by thedie lifting device 55 and the mold was completely closed. A pressure of200 tons was being applied to upper die 42 by the die lifting device 55.Further, the upper die 42 and the lower die 43 are heated almostuniformly and constantly at 100° C. by temperature controller 60 (FIG.12).

As shown in FIG. 10, the resin injection line provided on lower die 43(for example, at the position of resin injection tube 46) is formed byresin injection tube 46 communicating with resin injection path 65 viadivergent tube 64 and interposed with injection valve 46 b on the way,resin injection runner 46 c for storing the resin injected from theresin injection tube at a pressurized condition temporarily at aline-like condition, and resin injection film gate 46 d (clearancerelative to the upper die: 0.5 mm) for communicating with the runner 46c and injecting the resin into the cavity. In a similar manner, as shownin FIG. 9, other resin injection tubes 47, 48 disposed symmetrically ata pair condition are provided. Further, the resin discharge line isformed by resin discharge tube 49 communicating with resin dischargepath 67 and interposed with resin discharge valve 49 b on the way, resindischarge runner 49 c communicating with the resin discharge tube andstoring the discharged resin temporarily at a line-like condition, andresin discharge film gate 49 d (clearance relative to the upper die: 0.5mm) for communicating with the runner 49 c and discharging the resinfrom the cavity together with gas, etc., and it is provided on a singleside.

Consequently, substantially almost the entire circumference of thecavity is surrounded by the resin injection line and the resin dischargeline. Further, the length of the resin injection line is nearly fivetimes the length of the resin discharge line.

Tubes made of “Teflon” (registered trade mark) each having a diameter of12 mm and a thickness of 1.5 mm were used as resin injection path 65 andresin injection tubes 46-48 shown in FIG. 11. On the other hand, tubesmade of “Teflon” (registered trade mark) each having a diameter of 16 mmand a thickness of 2 mm were used as discharge path 67 and dischargetube 49. To prevent the resin from flowing into vacuum pump 58, resintrap 59 was provided on the way of discharge path 67.

Further, to seal between resin injection tubes 46-48 or discharge tube49 and lower die 43, rubber members for seal 46 a-49 a are disposed, andto maintain a tight condition between the upper and lower dies, a moldseal member (O-ring) 45 is disposed, on the outer circumference of thecavity, respectively.

In the above-described molding device, after air in the mold (in thecavity portion) is discharged from resin discharge port 49 by vacuumpump 58 and the pressure in the mold is confirmed to be reduced down to0.1 MPa or less by a vacuum pressure meter (not shown), the injection ofthe epoxy resin pressurized by resin injection device 57 havingpressurization device 62 is started. The pressurization device 62 usessyringe pumps 62 a, 62 b, and it is structure so as to prevent back flowof the resin to the tank side at the time of resin injection. The usedresin is a liquid epoxy rein prepared by mixing “Epicoat” 828 (an epoxyresin produced by Yuka Shell Epoxy Corporation) as its main ingredientand TR-C35H (imidazole derivative) of a blend produced by TorayIndustries, Inc. as its curing agent. The characteristic ofviscosity-time at the mold temperature, that is, at a moldingtemperature of 100° C., in more detail, the value of cure index, whichis used as an index for tracing a curing profile of the resin duringviscosity change of epoxy resin composition, is shown in FIG. 12A. Fromthis graph, the resin becomes more than 90% in cure index in a time ofabout 6 minutes, and reaches a condition capable of being removed fromthe mold.

In resin injection device 57, while main ingredient 61 a and curingagent 61 b are stirred beforehand, the resin is heated at 60° C. toreduce the viscosity down to a predetermined viscosity, and removal ofbubbles is carried out by vacuum pump 58.

Because air in the stirred resin mixing unit and air in the hose forresin injection path enter into the mold at the initial time of resininjection, the resin was not flown into the mold, the resin mixed withair was wasted from a divergent path (not shown), and after it wasconfirmed that air was not mixed in the resin, the pressurized resin wasinjected into the mold. Further, the discharge condition of each syringepump 62 a, 62 b of the pressurization device was set at 50 cc/stroke.After the initial resin mixed with gas was wasted, the resin wasinjected into the mold by opening injection valve 46 b after confirmingthe injection resin pressure (0.6 MPa) by an injection pressure sensor(not shown) disposed on resin injection path 65. At the time of startingthe injection, discharge valve 49 b of discharge tube 49 was opened.

After a time of 1 minute and 30 seconds passed from the start of theresin injection from resin injection tube 46, valve 47 b of resininjection tube 47 was opened, and the resin injection from the resininjection tube 47 was started. Then, after a time of 1 minute furtherpassed, valve 48 b of resin injection tube 48 was opened, and the resininjection from the resin injection tube 48″ was started.

During that, as the operation for accelerating impregnation of the resininto the reinforcing fiber substrate and efficiently removing a fineamount of bubbles stored in the substrate, the opening/closing operationof discharge valve 49 b was carried out four times using a vice grip.

After a time of 3 minutes and 30 seconds passed from the start of theresin injection from resin injection tube 46, the resin flowed out intodischarge tube 49. Then, after the resin was flown out for about 30seconds as it was, valve 49 b of discharge tube 49 was closed. It wasabout 4 minutes after the start of resin injection.

At the above-described state where the resin injection and impregnationwas completed, the resin pressure of 0.6 MPa was kept for 30 seconds,and thereafter, the heating condition was maintained for 12 minutes, andthen, the molded product was taken out from the mold.

When the appearance over the entire area of the molded product wasdetermined, there were not voids and pinholes at all, and it was a goodproduct extremely excellent in design quality.

Comparative Example 1

As Comparative Example 1, in a case where, using the above-describedmolding device and under the above-described conditions, the resin wasnot at all injected from resin injection tubes 47, 48 (runners 47 c, 48c and film gates 47 d, 48 d were closed) and the molding was carried outonly by the resin from resin injection tube 46, about 11 minutes wasrequired for the resin injection and impregnation, and non-impregnatedportion of about 400 cm² was generated near the discharge portion.

Example 3

Although the above-described Example 2 employed a single plate structureof reinforcing fiber substrate, as another example, when employed was acarbon fiber reinforcing structural material including a foam core(thickness: 10 mm, apparent specific gravity: 0.1) therein (three pliesof the above-described carbon fiber “TORAYCA” cloths were stacked oneach of the upper and lower surfaces of the foam core), an almostsimilar molded product excellent in surface quality could be obtained.The time for impregnation was about 4.5 minutes, and was a short periodof time similarly to the above-described example.

Next, an RTM molding method according to a third embodiment will beexplained. First, the production of the fiber reinforced resin molded bythis RTM molding method will be explained referring to FIG. 18. As shownin FIG. 18A, a resin injection port 85 and a suction port 86 areprovided on an upper die 83 of the double-sided mold. Lower die 84 has arunner for resin injection 88 and a runner for suction 89, and a sealgroove 90 is formed around the cavity. These upper and lower dies 83, 84are being heated up to a predetermined temperature. After preformsubstrate 87 as the reinforcing fiber substrate is placed on the cavitysurface of lower die 84, upper die 83 is lowered, and the substrate isset in the cavity formed with the upper die and the lower die 84. As thestructure of this preform substrate, as shown in FIG. 13 and FIG. 15, arandom mat layer is disposed immediately under the continuous fibersubstrate of the surface layer.

At such a condition, as shown in FIG. 18B, resin injection route 93communicating with resin tank 91 is closed by valve 92, and suctionroute 96 communicating with vacuum pump 94 is opened by valve 95. Then,the inside of the cavity is sucked at a vacuum condition through suctionport 86 and runner for suction 89 communicating with the suction route96. Thereafter, at a condition where the valve 95 of the suction routeis opened, the valve 92 of the resin injection route 93 is opened, whilethe matrix resin in resin tank 91 is pressurized by the pump, the resinis injected into injection port 85 through the resin injection route 93,and the resin is injected at a pressurized condition from the runner forresin injection 88 into the cavity. When the resin flows over the entirearea of the cavity and is impregnated into the reinforcing fibersubstrate 87 over its entire area and an excessive resin flows out tosuction route 96 through suction port 86 together with bubbles residentin the cavity, particularly in the reinforcing fiber substrate, thevalve 95 of the suction route 96 is closed, the resin pressure (staticpressure) is applied to the inside of the closed cavity for a while,thereby ensuring the impregnation. Then, the valve 92 of the resininjection route 93 is closed, and the resin is cured by maintaining theheating condition for a predetermined period of time.

Thereafter, as shown in FIG. 18C, upper die 83 is lifted, and moldedproduct 97 left on lower die 84 is taken out from the mold. The methodfor producing the fiber reinforced resin can be applied to other methodssuch as a vacuum molding method, a prepreg/autoclave curing method, anRFI (Resin Film Infusion) or a semipreg/oven heat curing method.

By the above-described production method, the fiber reinforced resin wasproduced as follows.

Example 4

As shown in FIG. 13, when a fiber reinforced resin 71 was produced, 1ply of “TORAYCA” T300 woven fabric CO6343B (weight: 200 g/m²) producedby Toray Industries, Inc. was placed as a surface layer 72 (continuousfiber layer), and as a layer immediately under the surface layer, arandom mat layer 73 made of glass fibers (weight: 70 g/m²) was disposed.Thereunder, a reinforcing fiber substrate 74 with a three-layerstructure (“TORAYCA” T700 woven fabric BT70-30 produced by TorayIndustries, Inc., weigh t: 300 g/m²) was disposed as a reinforcing layerto form the preform substrate 87. Using this preform substrate 87, aCFRP (carbon fiber reinforced plastic) was molded by the RTM moldingmethod shown in FIGS. 18A-18C. At that time, the temperature of the mold(formed by the upper die 83 and the lower die 84) was 95° C., and theepoxy resin 75 kept at 60° C. was injected at a pressurized resinpressure of 0.6 MPa from the resin tank 91 having a vacuum degassingfunction, and the molding was carried out. Where, the resin tank 91 isformed from a tank for a main ingredient of epoxy resin and a tank for acuring agent.

The resin flow state in the above-described RTM molding will beexplained based on FIG. 14 which is an enlarged view of the portion A ofFIG. 18B. The epoxy resin 75 flown out from resin tank 91 is chargedinto runner for resin injection 88 provided on the lower die throughresin injection port 85, and thereafter, the resin flows into the cavityfrom the runner 88 through the film gate which is a gap (about 1 mm)formed between the cavity and the runner 88. At that time, although theresin flows from the entire area in the thickness direction of thesubstrate 87, because the region of the random mat layer is lower indensity than the region formed with the carbon fiber woven fabric andlower in flow resistance, the resin begins to flow mainly through therandom mat layer 73. Because the carbon fiber woven fabric 72 disposedas a substrate for design is directly pressed to the upper die 83 andthere is almost no gap between the woven fabric 72 and the upper die 83,the injected resin flows toward the upper die 83 mostly as the resinflown from the random mat layer 73 rather than the resin flowing throughthe gap, and this resin flows into the gap between the woven fabric 72and the upper die 83. By this, even if the inside of the cavity wassucked at a vacuum condition, bubble 78 left in the weave textureportions of the woven fabric 72 and the gap between the woven fabric 72and the upper die 83 were discharged to the outside of the cavity by theflow along the stream lines 75 a to 75 b. In particular, as shown inFIGS. 17A and 17B, residual bubbles 82, which have not been released,are likely to stay at the cross threaded points of warp yarns 72 c andweft yarns 72 d forming the woven fabric 72. Such bubbles weredischarged to the outside of the cavity together with theabove-described resin flow, thereby preventing occurrence of voids andpinholes.

Example 5

Although the above-described Example 4 was carried out as to a casewhere the design surface was only one surface, a fiber reinforced resin76 as shown in FIG. 15 was molded. Namely, even in a case where aplurality of surfaces (in FIG. 15, upper and lower surfaces) are designsurfaces and a high surface quality is required for all the surfaces,similarly to the above-described manner, it is preferred that random matlayers (73 a, 73 b) made of glass fiber mat with a weight of 30 g/m² isdisposed immediately under the surface reinforcing fiber substrates (72a, 72 b) forming the design surfaces, and the resin is injected atconditions similar to those described above. As shown in FIG. 16 whichis an enlarged view of the portion A of FIG. 18B, by the flow from thestream line 75 a to 75 b and the flow from the stream line 75 c to 75 d,the resin having been flown through the random mat layers 73 a and 73 bflowed efficiently into the respective gaps between the surfacesubstrate 72 a and the upper die 83 and between the opposite-sidesurface substrate 72 b and the lower die 84, and while the resin flowedwithout gap and the residual bubbles 78, 79 were discharged, the resinwas filled and impregnated over the entire area. Therefore, for both thesurface side and the back surface side, the bubbles were discharged tothe outside of the cavity together with the above-described resin flows,and occurrence of void and pinholes could be prevented.

Example 6

As shown in FIG. 19, a sandwich structural material, wherein apolyurethane foam core 101 was provided in the central portion, on bothsurfaces a plurality of “TORAYCA” T300 woven fabrics CO6644B (weight:300 g/m²) produced by Toray Industries, Inc. were stacked as reinforcinglayers 74 a, 74 b, further thereon random mat layers 73 a, 73 b made ofglass fibers (weight: 50 g/m²) were disposed, and “TORAYCA” T300 wovenfabrics CO6343B (1 strand: 3K system, weight: 300 g/m²) produced byToray Industries, Inc. were disposed as the respective outermost surfacelayers, was molded to a fiber reinforced resin 100 by the RTM moldingmethod shown in FIG. 18A to FIG. 18C. The temperature of the mold (upperdie 83, lower die 84) was set at 85° C. In the figure, symbols 77 a, 77b indicate the epoxy resin injected, impregnated and cured. As a result,an FRP structural material having a sandwich structure could be moldedparticularly with a good surface quality (both surfaces).

Comparative Example 2

As comparison with the above-described Examples, the random mat layer73, which was disposed immediately under the surface layer 72 in Example4, was removed, and the other fiber structure of the surface layer andthe reinforcing fiber layer was set at the same structure. Further, RTMmolding was carried out by completely the same molding conditions asthose in the RTM molding method of Example 4.

In the result of the molding, because the random mat layer with a smallresin flow resistance did not exist, the time when excessive resinflowed out to the suction port 86 after start of resin injection wastaken long to be 1.38 times as compared with that in Example 4, but themolded product could be obtained. However, as shown in FIG. 17B, manypinholes 82, which had not been seen in Example 4, appeared at theportions of the weave texture and the cross threaded points of warpyarns and weft yarns, and it was not a good product in surface designquality.

In the above-described RTM molding method and device, to improve thesealability at the resin injection part and/or the resin discharge part,the following structure can be employed. Although the device stands onthe basis of assuming the aforementioned divided areas, the followingexplanation will be taken as to a simple molding model referring toFIGS. 20 to 23. This seal structure explained referring to FIGS. 20 to23 can be applied to the RTM molding method and device, in particular,to the RTM molding method and device according to the aforementionedfirst and second embodiments.

Namely, in this structure, the tube for resin injection and/or the tubefor resin discharge are provided at a condition nipped at the portionsof the parting surfaces, and the portion between the tube and the die issealed via an elastic material, and preferably, an end portion of anO-ring for sealing the cavity of the mold at positions of partingsurfaces of dies is incorporated into the elastic material for seal. Bynipping and fixing the tube for resin injection and/or the tube forresin discharge, for example, the resin injection member or the resindischarge member can be easily set or cleaned without using throughholes for resin injection opened on the mold or sleeves, andconsequently, the molding cycle can be shortened and a more efficientmolding becomes possible. Further, by using cheap resin tubes as theabove-described tubes and discarding the tubes after molding as theyare, the cleaning operation can be greatly saved, and it can contributeto a cost down due to reduction of amount of operation. Furthermore, byusing the elastic material for seal, keeping of a vacuum condition inthe cavity and maintaining the vacuum during the molding can be madesure, and at the same time, because resin leakage can also be prevented,a high-quality product with no voids and no pinholes can be obtained.

FIG. 20 is a perspective view of upper and lower dies 111, 112, FIG. 21is an enlarged sectional view of the lower die, and FIG. 22 shows tubefor resin injection • discharge 30 attached between the upper and lowerdies, respectively. As shown in FIG. 20, a reinforcing fiber substrate122 given with a product shape beforehand is placed in a molding cavity113 of a lower die 112 in which an O-ring 121 is disposed at the outercircumference of the cavity 113 formed on the upper surface of the lowerdie 112. Next, on grooves 120, 120′ having semi-cross sectional shapesof tube for resin injection 116 and tube for resin discharge 117communicating with runner for resin injection 114 and runner for resindischarge 115 and on grooves formed on elastic materials 118, 119provided on the ways of the grooves 120, 120′, made of a rubber (forexample, made of NBR) and communicating with the grooves 120, 120′,resin injection members 140 as shown in FIG. 22, in each of which ametal tube 142 is inserted into a tube 141 coming into contact with thegroove and is wound with a seal tape 143 around the outer surface at itstip portion, are disposed. Then, upper die is closed, the upper die 111is pressed toward lower die 112, and the above-described resin injectionmembers 140 are nipped. At such a state, hot water is filled in thepipes (not shown) provided in the mold to elevate in temperature thewhole of the mold.

Then, after the inside of cavity 113 is set at a vacuum condition viatube for resin discharge 117 connected to a vacuum trap (not shown)communicating with a vacuum pump (not shown), the resin is injected at apressurized condition into the cavity 113 via tube for resin injection116. After completing the resin injection, the tube for resin injection116 and the tube for resin discharge 117 are closed, and then, after theresin is heated and cured by the mold for a predetermined period oftime, the mold is opened, and the FRP product is taken out.

Further, as another structure for improving the sealability is shown inFIG. 21, a reinforcing fiber preform material 123 having a sandwichstructure, in which a core material 124 processed in a shape of aproduct and made of a foamed material covers the outer surface of areinforcing fiber substrate 125, is placed in a molding cavity 133formed by an upper die 131 and a lower die 132 disposed with elasticmaterials for seal 136, 137 communicating with an O-ring (not shown)disposed on the outer circumference of the cavity 133, and a tube forresin injection 134 and a tube for resin discharge 135 communicating arunner for resin injection 138 and a runner for resin discharge 139 arenipped by the upper and lower dies to seal them by bringing them intocontact with the above-described elastic materials for seal 136,137.

For the above-described tube for resin injection 134 and tube for resindischarge 135, for example, metal tubes are used. At such a condition,the mold is heated by flowing hot water in pipes (not shown) provided inthe mold. Thereafter, similarly to that in the example shown in FIG. 20,after the inside of cavity 133 is set at a vacuum condition via tube forresin discharge 135 connected to a vacuum trap communicating with avacuum pump, the resin is injected at a pressurized condition into thecavity 133 via tube for resin injection 134. After the pressurized resinis filled in runner for resin injection 138, the resin flows into cavity133 disposed with the above-described reinforcing fiber preform material123 through a film gate for injection 126, and the resin is impregnatedinto the reinforcing fibers of the reinforcing fiber preform material123. During that, excessive resin flows out to a vacuum trap throughtube for discharge 135 after being filled in runner for resin discharge139 through a film gate for discharge 127. After completing the resininjection, the tube for resin injection 134 and the tube for resindischarge 135 are closed, and then, after the resin is heated and curedat that condition for a predetermined period of time, the mold isopened, and a hat-like high-rigidity FRP sandwich structural material isobtained.

FIG. 22 shows an example of the structure of tube for resin injection116 or tube for resin discharge 117 used in the above-describe Example.Metal tube 142 is inserted into the tube for resin injection or the tubefor resin discharge made of a resin, and seal tape 143 is applied to theouter surface. The metal tube 142 is not deformed by grooves 10, 10′processed in a shape of a semi-circle (smaller than the radius of theabove-described respective tubes) on the upper and lower dies andelastic materials for seal 118, 119 when upper die 111 and lower die 112are closed and the tube for resin injection (described as symbol 31) orthe tube for resin discharge is nipped by the upper die and the lowerdie, and it exhibits an effect for maintaining the circular sectionalshape of the tube for resin injection 116 or the tube for resindischarge 117 and smoothing the vacuum suction from the inside of thecavity and the resin flow.

Further, seal tape 143 enhances the sealability of the elastic materialfor seal by bringing the seal tape 143 into contact with the elasticmaterial for seal when the upper die and the lower die are closed andthe tube for resin injection or the tube for resin discharge is nippedby the upper die and the lower die, thereby improving the vacuummaintenance ability in the cavity stably. It is possible to omit it in acase where the elastic material for seal is disposed to each of theupper die and the lower die.

Although a plastic tube such as nylon, polyethylene, polypropylene or afluorine contained resin such as “Teflon” (registered trade mark) can beused for the tube for resin injection or the tube for resin discharge, ametal tube made of iron, aluminum, brass, copper, stainless steel, etc.also can be used.

Further, for metal tube 142 inserted into the tip portion of the tubefor resin injection or the tube for resin discharge, iron, aluminum,brass, copper or stainless steel is used. Further, a plastic tube suchas ABS, polyethylene, polypropylene, nylon, vinyl chloride, acrylic,etc. also can be used. In any tube, the thickness is preferably 0.5 mmor more.

Furthermore, for seal tape 143 applied to the outer surface of the tipportion of the tube for resin injection or the tube for resin discharge,a tape made of a resin such as a fluorine contained resin such as“Teflon” (registered trade mark), nylon, polyester, polypropylene, etc.can be used. It is possible to omit it in a case where the elasticmaterial for seal is disposed to each surface of the upper die and thelower die.

FIGS. 23A to 23F show a plurality of examples of relationships betweenthe tube for resin injection and the tube for resin discharge and theelastic material for seal as cross-sectional views. For O-ring 154 andelastic material for seal 153, NBR, a fluorine contained resin such as“Teflon” (registered trade mark), etc. can be used, and a solid type ora hollow type can be used. Further, a foam material made of such resinsalso can be used.

Elastic material for seal 153 disposed on upper die 151 or lower die152, or on both, ensures the sealability by projecting it slightly fromthe die surface provided with it, and generating a reactive forcebetween the elastic material for seal 153 and the upper die 151 and thetube for resin injection 150 (or the tube for resin discharge) when theupper die 151 is closed and the elastic material for seal 153 is pressedand compressed by the die surface of the upper die 151.

Furthermore, by incorporating the end portion of O-ring 154 into elasticmaterial for seal 153, the elastic material for seal 153 and the O-ring154 are pressed to each other by the reactive force generated in thecompressed elastic material for seal 153 and O-ring 154 when upper die151 is closed, and while the continuous property of the seal (O-ring) ismaintained, the vacuum condition in the cavity is ensured.

Hereinafter, the method for sealing the tube for resin injection and thetube for resin discharge will be explained using FIGS. 23A to 23F.

In the structure shown in FIG. 23A, a groove, having a curved surfacewith a curvature equal to the curvature of the above-described tube forresin injection 150 (or the tube for resin discharge) or smaller thanthe curvature of the tube for resin injection 150, is formed in theelastic material for seal 153, the elastic material for seal 153 onO-ring 154 is disposed in the upper die 151 and/or the lower die 152with a portion processed at a shape corresponding to the elasticmaterial for seal, the portion disposed with the tube for resininjection or tube for resin discharge 150 is cut at the center of theO-ring 154, and at a state where the elastic material for seal 153 isdisposed in the upper die 151 and/or the lower die 152 with a portionprocessed at a shape corresponding to the elastic material for seal, thetube for resin injection or tube for resin discharge 150 is nipped bythe upper die 151 and the lower die 152. At that time, by incorporatingthe end portion of the O-ring 154 into the elastic material for seal153, the vacuum maintaining property in the cavity is ensured and aresin leakage is prevented.

In the structure shown in FIG. 23B, a groove, having a curvature equalto or smaller than the curvature of the above-described tube 150, isformed on each of the elastic material for seal 153 and the upper die151, the elastic material for seal 153 on O-ring 154 is disposed in thelower die 152 with a portion processed at a shape corresponding to theelastic material for seal, the closed loop of O-ring 154 is cut at anO-ring extending position disposed with the tube for resin injection ortube for resin discharge 150, and at a state where the elastic materialfor seal 153 is disposed in the lower die 152 with a portion processedat a shape corresponding to the elastic material for seal, the tube forresin injection or tube for resin discharge 150 is nipped by the upperdie 151 and the lower die 152. At that time, by incorporating the endportion of the O-ring 154 into the elastic material for seal 153, aresin leakage is prevented.

In the structure shown in FIG. 23C, the closed loop of O-ring 154 is cutat an O-ring extending position at which the tube for resin injection ortube for resin discharge 150 is also disposed on the upper die 151 orthe lower die 152 formed with a groove having a curvature equal to orsmaller than the curvature of the above-described tube 150, and bybringing the cut portion of the O-ring 154 into contact with the usedtube, the vacuum maintaining property in the cavity is ensured and aresin leakage is prevented.

In the structure shown in FIG. 23D, upper die 152 formed with a groovehaving a curvature equal to or smaller than the curvature of theabove-described tube 150, and elastic material for seal 153 formed as acontinuous material of O-ring 154, are provided, the tube for resininjection or tube for resin discharge 150 is nipped, the vacuummaintaining property in the cavity is ensured and a resin leakage isprevented.

In the structure shown in FIG. 23E, a groove, having a curvature equalto or smaller than the curvature of the above-described tube 150, isformed on the upper die 151, O-ring 154 provided as a continuousmaterial is disposed across the groove processed on the lower die 152for disposing the tube for resin injection or tube for resin discharge150 at a curvature equal to or larger than the curvature of the tube forresin injection or tube for resin discharge 150, and by disposing thetube for resin injection or tube for resin discharge 150 on the O-ring154 and nipping it by the upper die 151 and the lower die 152, thevacuum maintaining property in the cavity is ensured and a resin leakageis prevented.

In the structure shown in FIG. 23F, a state without the upper die ofFIG. 23A or FIG. 23B is shown, it is a plan view observing therelationship between elastic material for seal 153 and O-ring 154 forthe upper side of the parting surface.

Thus, with respect to the portion of the tube for resin injection or thetube for resin discharge, various structures for improving thesealability can be employed.

Further, in the aforementioned RTM molding method and device, to enableto discharge small bubbles present in gaps of the substrate, etc.,bubbles due to the evaporation of dissolved gas in the resin which aregenerated by reduction in pressure during resin injection, or finebubbles staying in the corner portions of the mold, the followingstructure can be employed. Namely, a structure can be employed fordischarging gas in the mold and excessive resin intermittently whileinjecting the resin into the mold at a pressurized condition, and bythis, it becomes possible to cause the resin flow to adequately pulsateand to accelerate the discharge of the bubbles in the resin. In thisstructure, as to a resin pressure Pm in the mold and a resin dischargepressure Pi at an injection port, the flow rate of the resin flowinginto the mold can be controlled by selective control between conditionsof Pm=Pi and Pm<Pi, and the resin flow rate also can be controlled byadjustment of a diameter of a discharge port for discharging the resin.Further, a structure also can be employed wherein the adjustment of thediameter of the discharge port and a timing for the adjustment arestored in memory, and based on the stored information, the resin flowrate is automatically controlled.

In more detail, in a conventional method, a molding method has beenemployed wherein a reinforcing fiber substrate is disposed in a moldbeforehand and the mold is closed, at a condition where an injectionvalve is closed, the inside of the mold is sucked at a vacuum conditionby a vacuum pump through a discharge path communicating with an openeddischarge valve, the resin pressure in the mold Pm is reduced preferablyat 0.01 MPa or less, and successively, at a condition where thedischarge valve is closed, the injection valve is opened and the resinis injected at a pressurized condition until the resin is completelycharged into the mold from the resin injection path. In this method,however, because the discharge valve is being closed during resininjection, bubbles left in the weave textures of a woven fabricsubstrate provided as the reinforcing fiber substrate, bubbles left at aportion between laminated layers of the reinforcing fiber substrate, andfurther, bubbles generated by evaporation of gas dissolved in the resininjected into the mold in the heat molding process, are not discharged,and by a condition where such bubbles are molded as they are and finebubbles are left in the molded product, there has been a case causing agreat deterioration in quality of the product. In particular, in a casewhere such bubbles appear on the surface as voids and pits, it hasbecome a defective product for a product requiring a design quality. Tosolve such a deterioration in quality of the product and the problem ofoccurrence of a defective product, it is necessary to appropriatelydischarge the gas (bubbles) left in the mold and generated byevaporation even in the resin injection process.

Accordingly, in the above-described method, while the pressurized resinis injected from the injection port, for example, by opening/closing thedischarge valve provided on the discharge path or by changing thediameter, residual bubbles and excessive resin in the mold can beefficiently discharged intermittently. For example, in a case where thedischarge valve is completely closed while the injection valve is openedto inject the resin, the condition becomes injection pressure Pi=resinpressure in the mold Pm, although the impregnation into the reinforcingfibers is facilitated because the pressure of the resin flowing into themold is high, the staying bubbles are also compressed up to almost thesame pressure as the resin pressure and they are being mixed in theresin. When the discharge valve is opened at this condition, therelationship becomes resin injection pressure Pi>resin pressure in themold Pm, and the residual bubbles and the pressurized excessive resin inthe mold are discharged from the discharge port simultaneously.

By setting an opening/closing speed of the discharge valve preferably ata speed within one second, the pressure in the mold reduces at a time bythe opening/closing speed, and the residual gas expands rapidly. Then, aresin flow due to the pressure difference and in accordance with achange in volume of the gas is generated, the gas staying betweenreinforcing fiber substrates or in the corner portions of the moldcannot stay by this rapid resin flow, and the gas is discharged from thedischarge port. The higher the reduction speed of the pressure in themold Pm is, the quicker the change of the gas volume becomes, and byproviding the impactive flow to the resin around the gas, residual gasis easily removed from its staying place. The gas once left isdischarged integrally with the flow toward the discharge path. Next, thedischarge valve is closed, and the resin is supplied from the injectionvalve.

By repeating such an intermittent opening/closing operation of thedischarge valve (this operation is not always full opening/fullclosing), while the residual gas (bubbles) in the mold is discharged;finally the discharge valve is fully closed at a state of completing thedischarge, after a condition applied with the resin injection pressureis maintained for a while, the injection valve is also fully closed andthe resin filled in the mold is heated and cured. Although the resin ispressurized in this aspect, a similar effect can be obtained even bysetting the injection pressure Pi at an atmospheric pressure and settingthe inside of the mold at a negative pressure.

The method for thus changing the pressure in the mold from Pi or anegative pressure instantaneously can also be realized, for example, bya momentary switching between a vacuum pump connected to a resin trapand a air pressurizing pump. Further, a more efficient discharge ofbubbles is possible by controlling the speed for changing the resinpressure in the mold Pm by adjusting the opening degree of the dischargevalve provided on the discharge path.

Further, as to the above-described discharge valve, by storing in memorythe cycle of its opening/closing operation beforehand, for example, byinputting it in a computer beforehand, and by operating the valve basedon the stored information, the problems in the conventional molding canbe solved without increase of manpower.

Furthermore, by inputting the resin injection condition and an optimumopening/closing condition of the discharge valve in accordance with theresin flow condition in advance, an optimum resin flow in accordancewith a change of environment (temperature of atmosphere, etc.) and thelike can be realized.

By such a method, an FRP molded product, in which voids and pitsconcerning the surface design quality do not exist or are extremely fewthat has been difficult to be realized in the conventional method, canbe obtained. By this, desirable mechanical properties can be alwayssatisfied stably, an excellent surface quality can be obtained stably,and the production can be carried out with a yield better than that inthe conventional method.

Further, in the aforementioned RTM molding method and device, to mold aproduct with a high surface quality efficiently in a short period oftime, the following method can be employed. Namely, there are a verticalparting type and a horizontal parting type in RTM molds, and in thevertical parting type (frequently used for injection molding), there isan advantage that occurrence of voids and pits causing a problem onsurface quality of molded product is very few because the resin flow iseasily made uniform by the influence of gravity and bubbles in the moldare easily released by rising, but there is a big problem that theproductivity is low because it is difficult to set a fiber reinforcingsubstrate in the mold, namely, to dispose the substrate onto the cavitysurface of the mold without disturbance and to fix it onto the moldsurface and a much time is required therefor. On the other hand, in thehorizontal parting type, namely, in the structure where the mold isformed by upper and lower dies, there is an advantage that the settingof the reinforcing fiber substrate onto the mold surface is relativelyeasy and the setting time is short, but in a general resin injectionmethod, that is, in a case where the resin is pressurized at a pressureof 0.2 to 1.0 MPa and the resin is injected without particularlycontrolling the flow rate, the resin flows into the mold at a flow ratedepending on the pressure, the resin is charged into the mold in arelatively short period of time, however, there is a case where thereinforcing fiber substrate is disturbed by the resin flow, there occursan uniform flow with a high flow rate, and many voids and pits aregenerated on the surface of the molded product. In particular, in a casewhere the resin is injected at a high discharge pressure of 0.5 MPa ormore (therefore, at a high speed) to shorten the molding time or mold aproduct with a large area in a short period of time, a disturbance ofthe weave structure of the substrate (particularly, a plain weave wovenfabric) is liable to occur, and because the resin flows in the mold at ahigh speed, the flow resistance varies within the flowing region inaccordance with a fine unevenness in thickness or difference instructure of the substrate and a uniform flow cannot be maintained, andtherefore, there is a case where a large void is generated by occurrenceof a local forestalling of the resin flow and the like. Furthermore,there is a case where the resin actually flows up to the substrateportion, but, because the flow rate is high, for example, there is notime for release of gas present in the texture of the woven fabric andthe gas stays there, and the gas generates a surface defect as a pit. Insuch conventional molding condition and molding process causingreduction of quality in appearance concerning the design quality, it isdifficult to ensure a high surface quality while carrying out ahigh-speed injection for shortening the molding time. The larger thesize of a product to be molded becomes, the more frequently such adefect on quality in appearance is liable to occur, because a high-speedresin injection is to be inevitably employed.

Because the flow state of resin greatly influences generation of suchvoids and pits concerning design quality, the density of the reinforcingfiber substrate, that is, the weight thereof, also becomes an importantfactor. Namely, because a weight of reinforcing fibers per one layerinfluences a flow resistance of resin and easiness of gas release, it isnecessary to set a proper weight in accordance with the resin flowcondition. This proper weight has to be set from the viewpoints of notonly the surface quality but also the workability and utilization factorin strength of a preform. Namely, if the weight is too great and therigidity of the substrate becomes high, the reinforcing fiber substratebecomes hard to be situated along the mold surface and hard to be formedin a three-dimensional shape, and there is a case where it takes muchworking time to make a preform, or that at that time disturbance of thesubstrate occurs and the mechanical properties of the FRP molded productdecrease. Namely, to carry out an efficient production, there is aproper weight corresponding to the production conditions (molding size •shape, molding conditions, etc.).

Further, among molding conditions, particularly influence given to asurface quality by temperature and resin injection pressure is great. Ifa temperature of injected resin is high, the resin viscosity reduces andthe flowability of the resin increases, and although the impregnationproperty of the resin into the substrate is good, the flowabilityrapidly deteriorates by a high elevation rate of the viscosity, and whenthe molded product is big, there is a case where the flow of the resinreduces in speed on the way of the molding and it causes anon-impregnated portion. Even if the resin can flow over the entirearea, in an area in which the viscosity has become high, there is a casewhere many voids and pits are generated even though non-impregnatedportions are not generated. On the other hand, if there is an unevennessof the temperature of a mold or there is a change in the temperatureduring molding, there is a case where very fine bubbles remaining in themold come into contact with each other and they grow a big bubbledeveloping to a void or a pit. Further, it is important that thepressure is also adequate. There is a case where that a too highpressure causes an expansion in volume in a cavity to generate bubbles,or a too low pressure causes a state where residual bubbles cannot becompressed to be small.

Further, since a reactive gas may be generated from a reactive resin inits curing process, or fine gas (bubbles) having been contained in aresin may grow to voids or pits as the molding time passes, it is betterto cure the resin as quickly as possible after the resin is impregnatedinto the substrate. The influence given to the efficiency of the moldingby the characteristics of the material of the reactive resin is veryhigh, and for example, depending upon the kind of the curing agent, thereaction speed becomes maximum at an initial period of the reaction ofthe resin, and as the time passes, the reaction speed reduces, andtherefore, there is a case where the time required for curing becomeslong. On the contrary, if the curing time is to be shortened byelevating the temperature of the mold, there is a case where the initialviscosity increases too high, the viscosity is elevated too much at thetime of resin injection and flow, ultimately the resin is gelated, andthe molding is stopped on the way and a non-impregnated portion isgenerated.

Thus, in FRP molding (particularly, RTM molding), there exist propermolding conditions and material characteristic in accordance withmolding size (area), and if not molded at proper conditions, problems onquality, in particular, on surface quality, are liable to occur.

Accordingly, in the RTM molding method and device, in particular, tomold a product with almost no voids and pits and having a high surfacedesign quality efficiently in a short period of time, a method can beemployed wherein, when the resin is injected into the cavity of the moldat a pressurized condition, a ratio of a flow rate of the resin per aunit time (Q:cc/min.) to a projected area of the cavity (S:m²)(Q/S:cc/min.·m²) is in a range of 50<Q/S<600.

In this method it is preferred that the product of the above-describedratio (Q/S:cc/min.·m²) and a pressurizing force of the resin (P:MPa)((Q/S)×P:ccMPa/min.·m²) is in a range of 20≦(Q/S)×P≦400. Further, it ispreferred that the pressurizing force of the resin is in a range of 0.2to 0.8 MPa, and the resin is preferably cured for 3 to 30 minutes at aconstant heating temperature in a range of 60 to 160° C.

By such RTM molding conditions, a molded product, in which defects suchas voids and pits are not generated on the surface formed as a designsurface, that has been difficult to be realized by the conventional RTMmolding conditions, can be molded efficiently in a short period of timeand stably, and the molded product high in surface quality can beproduced at a high cycle and at a large scale.

INDUSTRIAL APPLICATIONS

The RTM molding method and device can be applied to any RTM moldingrequiring a high-speed molding and, in particular, the device is usefulto mold a relatively large product relatively complicated in shape,efficiently in a short period of time with an excellent surface quality,particularly for molding an excellent design surface.

In more detail, the device is suitable for a relatively large FRP panelmember for general industries having a product size of 1 m² or more, inparticular, for an outer panel member or a structural material forvehicles, and among these, it is suitable for RTM molding of an FRPmember used as an outer panel member highly requiring a design quality.The outer panel member for vehicles means a so-called panel member suchas a door panel or a food in a car or a truck, a roof, a trunk lid, afender, a spoiler, a side skirt, a front skirt, a mud guard or a doorinner panel. In particular, it is suitable for a relatively large panelmember requiring a design quality. As other FRP panel members, areraised a member for aircraft, various panels in trains such as a door, aside panel or an interior panel, cover members for construction machinessuch as a crane, a partition, a door panel or a shield plate in aconstruction field, and further, an outer surface panel such as asurfboard or a skateboard in a sport field, or parts for bicycles.

1. An RTM molding method comprising the steps of disposing a reinforcingfiber substrate in a cavity of a mold consisting of a plurality of dies,clamping said mold, and thereafter injecting resin to complete molding,characterized in that divided areas with respect to a surface directionof said reinforcing fiber substrate are assumed, each divided area isone in which injected resin expands over the entire surface in said eachdivided area and can be substantially uniformly impregnated in athickness direction of said substrate, and resin introducing paths areformed for respective assumed divided areas for introducing the injectedresin into said respective divided areas, and wherein, after resin isimpregnated into said reinforcing fiber substrate by injecting the resinfrom a resin injection line toward a resin discharge line, which aredisposed on an outer circumference of said cavity, the resin is heatedand cured, and said resin injection line is divided into a plurality ofparts.
 2. The RTM molding method according to claim 1, wherein saidresin injection line and resin discharge line are formed substantiallyover the entire range of said outer circumference of said cavity.
 3. TheRTM molding method according to claim 1, wherein the length of saidresin injection line is two times or more the length of said resindischarge line.
 4. The RTM molding method according to claim 1, whereinsaid resin injection line and/or said resin discharge line is formedfrom a groove processed on said mold.
 5. The RTM molding methodaccording to claim 4, wherein said mold comprises an upper die and alower die, and said groove is all processed on said lower die.
 6. TheRTM molding method according to claim 1, wherein said resin dischargeline is also divided into a plurality of parts.
 7. The RTM moldingmethod according to claim 1, wherein resin injection from said resininjection line divided into a plurality of parts is carried out in orderfrom a resin injection line part which is substantially more distantfrom said resin discharge line.
 8. The RTM molding method according toclaim 1, wherein resin injection is carried out also from said resindischarge line by switching said resin discharge line to a resininjection line after a predetermined period of time.
 9. The RTM moldingmethod according to claim 1, wherein a core material is laminated tosaid reinforcing fiber substrate.
 10. The RTM molding method accordingto claim 1, wherein a tube for resin injection and/or a tube for resindischarge is provided being nipped between parting surfaces of dies, andportions between said tube and said dies are sealed with an elasticmaterial.
 11. The RTM molding method according to claim 10, wherein anend portion of an O-ring for sealing said cavity of said mold atpositions of parting surfaces of dies is incorporated into said elasticmaterial for seal.
 12. The RTM molding method according to claim 1,wherein, while resin is injected into said mold at a pressurizedcondition, gas and excessive resin in said mold are dischargedintermittently.
 13. The RTM molding method according to claim 12,wherein, when a resin pressure in said mold of resin pressurized andinjected is referred to as Pm and a resin discharge pressure at aninjection port for injecting resin is referred to as Pi, a flow rate ofresin flowing into said mold is controlled by selective control betweenconditions of Pm=Pi and Pm<Pi.
 14. The RTM molding method according toclaim 12, wherein a flow rate of resin flowing into said mold iscontrolled by adjustment of a diameter of a discharge port fordischarging resin.
 15. The RTM molding method according to claim 14,wherein said adjustment of said diameter of said discharge port and atiming for said adjustment are stored in memory, and based on the storedinformation, said flow rate of resin flowing into said mold isautomatically controlled.
 16. The RTM molding method according to claim1, wherein, when resin is injected into said cavity of said mold at apressurized condition, a ratio of a flow rate of resin per a unit time(Q:cc/min.) to a projected area of said cavity (S: m²) (Q/S:cc/min.·m²)is in a range of 50<Q/S<600.
 17. The RTM molding method according toclaim 16, wherein the product of said ratio (Q/S:cc/min.·m²) and apressurizing force of resin (P:MPa) ((Q/S)×P:ccMPa/min.·m²) is in arange of 20≦(Q/S)×P≦400.
 18. The RTM molding method according to claim16, wherein a pressurizing force of resin is in a range of 0.2 to 0.8MPa.
 19. The RTM molding method according to claim 16, wherein saidresin is cured for 3 to 30 minutes at a constant heating temperature ina range of 60 to 160° C.
 20. An RTM molding method comprising the stepsof disposing a reinforcing fiber substrate in a cavity of a moldconsisting of a plurality of dies, clamping said mold, and thereafterinjecting resin to complete molding, characterized in that divided areaswith respect to a surface direction of said reinforcing fiber substrateare assumed, each divided area is one in which injected resin expandsover the entire surface in said each divided area and can besubstantially uniformly impregnated in a thickness direction of saidsubstrate, and resin introducing paths are formed for respective assumeddivided areas for introducing the injected resin into said respectivedivided areas, wherein at least one surface layer of said reinforcingfiber substrate comprises a continuous fiber layer, and a layerpositioned immediately under said surface layer comprises a random matlayer.
 21. The RTM molding method according to claim 20, wherein saidsurface layer is formed from three or less continuous fiber layers. 22.The RTM molding method according to claim 20, wherein the total weightof said continuous fiber layer forming said surface layer is 700 g/m² orless.
 23. The RTM molding method according to claim 20, whereinreinforcing fibers of said surface layer are formed as a carbon fiberwoven fabric.
 24. The RTM molding method according to claim 20, whereinthe total weight of said random mat layer is 150 g/m² or less.
 25. TheRTM molding method according to claim 20, wherein said random mat layercomprises glass fibers.
 26. The RTM molding method according to claim20, wherein a core material is laminated to said reinforcing fibersubstrate.
 27. An RTM molding device for disposing a reinforcing fibersubstrate in a cavity of a mold consisting of a plurality of dies,clamping said mold, and thereafter injecting resin to complete molding,characterized in that divided areas with respect to a surface directionof said reinforcing fiber substrate are assumed, each divided area isone in which injected resin expands over the entire surface in said eachdivided area and can be substantially uniformly impregnated in athickness direction of said substrate, and resin introducing paths areformed for respective assumed divided areas for introducing the injectedresin into said respective divided areas and wherein, after resin isimpregnated into said reinforcing fiber substrate by injecting the resinfrom a resin injection line toward a resin discharge line, which aredisposed on an outer circumference of said cavity, the resin is heatedand cured, and said resin injection line is divided into a plurality ofparts.
 28. The RTM molding device according to claim 27, wherein saidresin injection line and resin discharge line are formed substantiallyover the entire range of said outer circumference of said cavity. 29.The RTM molding device according to claim 27, wherein the length of saidresin injection line is two times or more the length of said resindischarge line.
 30. The RTM molding device according to claim 27,wherein said resin injection line and/or said resin discharge line isformed from a groove processed on said mold.
 31. The RTM molding deviceaccording to claim 30, wherein said mold comprises an upper die and alower die, and said groove is all processed on said lower die.
 32. TheRTM molding device according to claim 27, wherein said resin dischargeline is also divided into a plurality of parts.
 33. The RTM moldingdevice according to claim 27, wherein resin injection from said resininjection line divided into a plurality of parts is carried out in orderfrom a resin injection line part which is substantially more distantfrom said resin discharge line.
 34. The RTM molding device according toclaim 27, wherein resin injection is carried out also from said resindischarge line by switching said resin discharge line to a resininjection line after a predetermined period of time.
 35. The RTM moldingdevice according to claim 27, wherein a core material is laminated tosaid reinforcing fiber substrate.
 36. The RTM molding device accordingto claim 27, wherein a tube for resin injection and/or a tube for resindischarge is provided being nipped between parting surfaces of dies, andan elastic material for seal is interposed between said tube and saiddies.
 37. The RTM molding device according to claim 36, wherein an endportion of an O-ring for sealing said cavity of said mold at positionsof parting surfaces of dies is incorporated into said elastic materialfor seal.
 38. The RTM molding device according to claim 27, whereinmeans for, while injecting resin into said mold at a pressurizedcondition, discharging gas and excessive resin in said moldintermittently is provided.
 39. The RTM molding device according toclaim 38, wherein, when a resin pressure in said mold of resinpressurized and injected is referred to as Pm and a resin dischargepressure at an injection port for injecting resin is referred to as Pi,means for controlling a flow rate of resin flowing into said mold byselective control between conditions of Pm=Pi and Pm<Pi is provided. 40.The RTM molding device according to claim 38, wherein means forcontrolling a flow rate of resin flowing into said mold by adjusting adiameter of a discharge port for discharging resin is provided.
 41. TheRTM molding device according to claim 40, wherein means for storing inmemory said adjustment of said diameter of said discharge port and atiming for said adjustment, and based on the stored information,automatically controlling said flow rate of resin flowing into saidmold, is provided.
 42. The RTM molding device according to claim 40,wherein said means for adjusting said diameter of said discharge portcomprises a valve opening/closing device.